Bending angle measuring device and bending angle measuring method

Abstract

A laser diode (34) emits linear laser light onto a first flange and a second flange of a workpiece bent to a target bending angle, the first flange and the second flange being on the front side and the rear side of the workpiece, respectively, with respect to a punch and a die. A camera (35) captures an image of reflected light due to reflection of the laser light emitted onto the first and second flanges. An image angle calculation unit (33) extracts, as a straight line part, a range of high-luminance points obtained by excluding high-luminance points due to the emission of light onto a region in which the first or second flange is a curved surface from a plurality of high-luminance points obtained by sampling a line image formed from the reflected light included in the image captured by the camera (35), and calculates an image angle of a straight line obtained by linearly approximating at least the sampled high-luminance points included in the straight line part. A bending angle conversion unit (22) converts the image angle into the bending angle of the workpiece.

Description

Bending Angle Measuring Device and Bending Angle Measuring Method

[0001] The present disclosure relates to a bending angle measuring device and a bending angle measuring method.

[0002] A press brake includes an upper table on which a punch is mounted and a lower table on which a die is mounted. The upper table is lowered onto the lower table to sandwich and bend a workpiece placed on the die between the punch and the die. The press brake includes a bending angle measuring device for measuring the bending angle of the workpiece. There are contact type and non-contact type bending angle measuring devices, and Patent Document 1 describes a non-contact type bending angle measuring device.

[0003] Japanese Patent Application Laid-Open No. 2019-10666

[0004] Typically, a non-contact type bending angle measuring device irradiates a linear laser beam onto a workpiece, and a camera captures the reflected light of the laser beam irradiated onto the workpiece, and measures the bending angle of the workpiece based on the angle of the line image formed by the captured reflected light. The non-contact type bending angle measuring device can accurately measure the bending angle of the workpiece if the surface of the bent workpiece where the laser beam is irradiated is flat.

[0005] However, there may be a sag due to shearing at the end of the workpiece bent by the press brake. Sag is a roundness or depression formed at the end of the surface of the workpiece that has been sheared. When the workpiece is a thin plate such as 1 mm thick and long, the end of the workpiece may sag when the workpiece is bent by the press brake. Furthermore, a roundness called an R shape may be intentionally formed at the end of the workpiece. In such a case, a part of the surface of the workpiece where the laser beam is irradiated may be a curved surface. If a part of the surface of the workpiece where the laser beam is irradiated is a curved surface, an error occurs in the measured angle, and the bending angle of the workpiece cannot be accurately measured.

[0006] There is a need for the emergence of a bending angle measuring device and a bending angle measuring method that can accurately measure the bending angle of the workpiece even when a part of the surface of the workpiece where the laser beam is irradiated is a curved surface.

[0007] A first aspect of one or more embodiments provides a bending angle measuring device comprising: a laser beam irradiation unit that irradiates a linear laser beam onto a first flange on the front side and a second flange on the rear side of a punch and a die in a workpiece that is sandwiched between a punch and a die and bent to a target bending angle; a camera that photographs the reflected light of the laser beam irradiated onto the first and second flanges; an image angle calculation unit that extracts a range of high-brightness points as a straight line portion from a plurality of high-brightness points sampled from the line image of the reflected light contained in the image captured by the camera, excluding high-brightness points irradiated onto a region where the first or second flange is a curved surface, and calculates a straight line image angle obtained by linearly approximating at least the sampled high-brightness points contained in the straight line portion; and a bending angle conversion unit that converts the image angle into the bending angle of the workpiece.

[0008] A second aspect of one or more embodiments provides a bending angle measurement method which involves irradiating a first flange on the front side and a second flange on the rear side of a punch and a die in a workpiece that has been bent by being sandwiched between a punch and a die with linear laser light, capturing the reflected light of the laser light irradiated onto the first and second flanges with a camera, sampling the line image of the reflected light included in the image captured by the camera to obtain a plurality of high-brightness points, extracting the high-brightness points from the plurality of high-brightness points, excluding the high-brightness points irradiated onto the region where the first or second flange is a curved surface, generating a straight line by linearly approximating at least the high-brightness points included in the straight line, calculating the image angle of the straight line, and converting the image angle into the bending angle of the workpiece.

[0009] According to one or more embodiments of the bending angle measuring device and bending angle measuring method, the bending angle of a workpiece can be accurately measured even if a part of the surface of the workpiece irradiated with laser light is curved.

[0010] Figure 1 is a diagram showing an example of the overall configuration of a press brake equipped with a bending angle measuring device according to one or more embodiments. Figure 2 is a perspective view showing angle sensors positioned in front of and behind the punch and die. Figure 3 is a block diagram of a bending angle measuring device according to one or more embodiments. Figure 4 is a block diagram showing a specific example of the configuration of an image angle calculation unit included in the bending angle measuring device according to one or more embodiments. Figure 5 is a diagram showing a plurality of high-brightness points obtained by sampling line images included in a captured image taken by a camera included in the bending angle measuring device according to one or more embodiments of a laser beam irradiated onto the workpiece and die. Figure 6 is a diagram showing the peak brightness in the brightness distribution for each line of the captured image. Figure 7A is a diagram showing the step of determining the angle A12 between high-brightness point P1 and high-brightness point P2 among the plurality of high-brightness points shown in Figure 5, as part of a series of steps for extracting high-brightness points from a workpiece. Figure 7B is a diagram showing the step of determining the angle A23 between high-brightness point P2 and high-brightness point P3 among the plurality of high-brightness points shown in Figure 5, as part of a series of steps for extracting high-brightness points from a workpiece. Figure 7C shows the process of determining the angle A34 between high-brightness point P3 and high-brightness point P4, which are among the multiple high-brightness points shown in Figure 5, as part of a series of steps for extracting high-brightness points in a workpiece. Figure 7D shows the process of determining the angle A45 between high-brightness point P4 and high-brightness point P5, which are among the multiple high-brightness points shown in Figure 5, as part of a series of steps for extracting high-brightness points in a workpiece. Figure 8 shows an example of a method for extracting curved surface high-brightness points obtained by reflected light of laser light irradiated onto a curved region of the workpiece, from among the multiple high-brightness points shown in Figure 5. Figure 9 shows the state in which high-brightness points have been extracted as a straight line, excluding the curved surface high-brightness points from the workpiece high-brightness points. Figure 10 shows the state in which all high-brightness points included in the straight line shown in Figure 9 have been extracted. Figure 11 shows a straight line approximated by a straight line of all high-brightness points included in the straight line shown in Figure 10. Figure 12 shows the image angle of the straight line shown in Figure 11. Figure 13 shows another method for extracting the main reference point of the workpiece high-brightness points. Figure 14 is a flowchart illustrating the operation of a bending angle measuring device according to one or more embodiments, and a bending angle measuring method according to one or more embodiments.

[0011] Hereinafter, one or more embodiments of a bending angle measuring device and a bending angle measuring method will be described with reference to the attached drawings.

[0012] First, using Figure 1, an overall configuration example and a general overview of the operation of a press brake 100 equipped with a bending angle measuring device according to one or more embodiments will be described. As shown in Figure 1, the press brake 100 includes an NC (Numerical Control) device 10 that functions as a control device for controlling the press brake 100. The part excluding the NC device 10 and the bending angle measuring device described later will be referred to as the press brake body 101. The press brake 100 includes an upper table 1, a lower table 3, and left and right side plates 5R and 5L. An upper die holder 2 is attached to the upper table 1, and a lower die holder 4 is attached to the lower table 3.

[0013] The upper table 1 is configured to be raised and lowered by hydraulic cylinders 6L and 6R located on the left and right sides. The hydraulic cylinders 6L and 6R constitute the table lifting mechanism. The table lifting mechanism may include actuators other than the hydraulic cylinders 6L and 6R. The table lifting mechanism may also be composed of components other than the hydraulic cylinders 6L and 6R. The table lifting mechanism lowers the upper table 1 so that it is closer to the lower table 3, or raises it so that it is further away from the lower table 3.

[0014] The upper die holder 2 is fitted with the upper die, which is the punch Tp, and the lower die holder 4 is fitted with the lower die, which is the die Td. Figure 1 shows a modular type in which the upper die holder 2 is integrally attached along the entire length of the lower end of the upper table 1, but it may also be an intermediate plate type in which multiple intermediate plates for which punch Tp are attached are attached in the longitudinal direction of the lower end of the upper table 1. The intermediate plates are also upper die holders.

[0015] Mounting a punch Tp on the upper table 1 means mounting the punch Tp on the upper die holder 2 or the intermediate plate. Mounting a die Td on the lower table 3 means mounting the die Td on the lower die holder 4. Two or more punches Tp may be mounted side by side on the upper table 1, and two or more dies Td may be mounted side by side on the lower table 3.

[0016] A back gauge 40 is positioned on the underside of the lower table 3. The back gauge 40 includes abutments 42a and 42b that move left and right along the back gauge carriage 41. Here, there are two abutments, 42a and 42b, but the number of abutments is not limited to two. The abutments 42a and 42b are configured to move in the height direction and the front-to-back direction as well.

[0017] Before the operator places the sheet metal W, which is the workpiece to be processed, onto the die Td and bends the sheet metal W by sandwiching it between the punch Tp and the die Td, the abutments 42a and 42b move to positions corresponding to the die Td. The operator places the sheet metal W on the die Td so that its rear end abuts against the abutments 42a and 42b. In other words, the abutments 42a and 42b act to determine the front-to-back position of the sheet metal W when it is placed on the die Td.

[0018] An operating pendant 7 is attached to the left side of the press brake 100 via an arm 7a, and has a display unit 71 and an operating unit 72 including a plurality of operating buttons. The operating pendant 7 is connected to the NC device 10. The NC device 10 is connected to a foot switch 8 which has an open foot switch 81 for raising the upper table 1 and a close foot switch 82 for lowering the upper table 1. When the operator steps on the close foot switch 82, the upper table 1 is lowered, and the sheet metal W is bent by being sandwiched between the punch Tp and the die Td. When the operator steps on the open foot switch 81, the upper table 1 is raised, and the bent sheet metal W can be removed.

[0019] In Figure 1, the bending angle measuring device is not shown. As shown in Figure 2, angle sensors 30F and 30R, which constitute part of the bending angle measuring device, are positioned in front of and behind the die Td, respectively. In Figure 2, the punch Tp is not shown. The front angle sensor 30F and the rear angle sensor 30R have the same configuration. The angle sensors 30F and 30R are collectively referred to as angle sensor 30. In the configuration example shown in Figure 3, the angle sensor control device 20 and the angle sensors 30 constitute the bending angle measuring device. The angle sensor control device 20 includes a straight section angle conversion unit 21 and a bending angle conversion unit 22. The angle sensor control device 20 can be configured using computer equipment.

[0020] As shown in Figure 3, the angle sensor 30 comprises a sensor substrate 31, a laser diode 34, and a camera 35. The sensor substrate 31 has an operation instruction unit 32 and an image angle calculation unit 33. As shown in Figure 2, the housing 301 of the angle sensor 30 (30F and 30R) has a first housing section 315 for housing the sensor substrate 31 and the camera 35, and a second housing section 340 for housing the laser diode 34.

[0021] The laser diode 34 of the angle sensor 30F is housed in the second housing 340 and oriented toward the sheet metal W so as to irradiate the lower surface of the front flange Wf (first flange) of the sheet metal W with a linear laser beam (hereinafter referred to as line laser beam) shown by a dashed line. The laser diode 34 of the angle sensor 30R is housed in the second housing 340 and oriented toward the sheet metal W so as to irradiate the lower surface of the rear flange Wr (second flange) of the sheet metal W with a line laser beam. In Figure 2, the illustration of the line laser beam irradiated by the laser diode 34 of the angle sensor 30R onto the rear flange Wr is omitted. The laser diode 34 is an example of a laser beam irradiation unit.

[0022] The camera 35 captures the reflected light of the line laser beam irradiated onto the front flange Wf and the rear flange Wr from a position a predetermined distance away from the laser diode 34. The line laser beam may also irradiate the upper end of the die Td.

[0023] In Figure 3, when the NC device 10 controls the press brake body 101 to bend the sheet metal W to a predetermined target bending angle, it transmits a bending angle measurement request signal and the target bending angle to the angle sensor control device 20. The linear section angle conversion unit 21 of the angle sensor control device 20 converts the target bending angle into a linear section angle in principle. When the reflected light of the line laser beam irradiated onto the front flange Wf and rear flange Wr of the sheet metal W bent to the target bending angle is captured by the camera 35, the angle of the line image due to the reflected light included in the captured image is determined in principle. The linear section angle conversion unit 21 converts the target bending angle into a linear section angle that has been determined in advance to correspond to the target bending angle.

[0024] The angle of the straight line portion of the line image in the image captured by camera 35 is, for example, the angle with respect to the horizontal direction of the frame of the captured image.

[0025] The angle sensor control device 20 transmits an instruction signal to the operation instruction unit 32 of the sensor board 31, instructing it to irradiate with line laser light and capture reflected light. Upon receiving the instruction signal from the angle sensor control device 20, the operation instruction unit 32 instructs the laser diode 34 to irradiate with line laser light and instructs the camera 35 to capture reflected light. The linear section angle conversion unit 21 transmits the linear section angle to the image angle calculation unit 33. The image angle calculation unit 33 acquires the image captured by the camera 35 and calculates the image angle of the line image as described later.

[0026] As shown in Figure 4, the image angle calculation unit 33 includes a sampling processing unit 331, a linear section extraction unit 332, a linear all-pixel extraction unit 333, a linear approximation unit 334, and a linear angle calculation unit 335. The sampling processing unit 331 samples a line image by extracting peak brightness for each predetermined number of lines from all the lines constituting the input captured image. Figure 5 shows an example of the state in which the sampling processing unit 331 has sampled a line image in frame F of the captured image. In Figure 5 and Figures 7A and later described later, the number of lines from which peak brightness was extracted is shown to be less than the actual number for the sake of illustration simplification.

[0027] In Figures 5 and 7A to 8, the horizontal solid lines indicate lines from which peak brightness has been extracted in the captured image. By extracting the peak brightness of the selected line, the sampling processing unit 331 can extract pixels having high-brightness points P1 to P15. High-brightness points P1 to P3 are high-brightness points based on the reflected light of the line laser beam irradiated onto the upper end of the die Td. High-brightness points P4 to P15 are high-brightness points based on the reflected light of the line laser beam irradiated onto the front flange Wf or the rear flange Wr. As shown in Figure 6, high-brightness points P1 to P15 indicate pixels at horizontal positions where peak brightness was obtained in the brightness distribution for each line.

[0028] As shown in Figure 5, among the high-brightness points P4 to P15, the multiple high-brightness points on the P15 side are curved. This is because the multiple high-brightness points on the P15 side are high-brightness points based on reflected light from line laser beams irradiated onto a region where the front flange Wf or rear flange Wr is curved due to the sagging, drooping, or R-shape of the sheet metal W. High-brightness points based on reflected light from line laser beams irradiated onto a region where the front flange Wf or rear flange Wr is curved will be referred to as curved surface high-brightness points.

[0029] The linear section extraction unit 332 first excludes the high-brightness points P1 to P15 that are based on the reflected light of the line laser beam irradiated onto the die Td, and extracts the high-brightness points that are based on the reflected light of the line laser beam irradiated onto the front flange Wf or rear flange Wr, as follows. The high-brightness points based on the reflected light of the line laser beam irradiated onto the die Td will be called die high-brightness points, and the high-brightness points based on the reflected light of the line laser beam irradiated onto the front flange Wf or rear flange Wr will be called workpiece high-brightness points. The linear section extraction unit 332 sets the selected high-brightness point among the workpiece high-brightness points as a reference point (main reference point).

[0030] As shown in Figure 7A, the linear section extraction unit 332 uses, for example, the lowest high-luminance point P1 in frame F as a provisional reference point and calculates the angle A12 between high-luminance point P1 and high-luminance point P2 located one position above it. The linear section extraction unit 332 then calculates the difference between angle A12 and the linear section angle. Since the difference exceeds the allowable value, the linear section extraction unit 332 determines that high-luminance point P1 is a die high-luminance point. The allowable value can be set as appropriate.

[0031] As shown in Figure 7B, the linear section extraction unit 332 uses the high-luminance point P2 as a provisional reference point and calculates the angle A23 between the high-luminance point P2 and the high-luminance point P3 located one position above it. The linear section extraction unit 332 then calculates the difference between angle A23 and the linear section angle. Here again, the difference exceeds the allowable value, so the linear section extraction unit 332 determines that the high-luminance point P2 is a die high-luminance point. Similarly, in the angle A34 between the high-luminance points P3 and P4 shown in Figure 7C, the difference between angle A34 and the linear section angle exceeds the allowable value. Therefore, the linear section extraction unit 332 determines that the high-luminance point P3 is a die high-luminance point.

[0032] As shown in Figure 7D, the linear section extraction unit 332 uses the high-brightness point P4 as a provisional reference point and calculates the angle A45 between the high-brightness point P4 and the high-brightness point P5 located one position above it. The linear section extraction unit 332 then calculates the difference between angle A45 and the linear section angle. Here, since the difference does not exceed the allowable value, the linear section extraction unit 332 determines that the high-brightness point P4 is a workpiece high-brightness point. The linear section extraction unit 332 sets the high-brightness point P4 as the main reference point. The linear section extraction unit 332 may also set a high-brightness point P5, for example, one position above the high-brightness point P4, as the main reference point. The linear section extraction unit 332 determines that the high-brightness point P4 and the high-brightness points P5 to P15 located above it are workpiece high-brightness points.

[0033] As shown in Figure 8, the linear section extraction unit 332 calculates the angles A45 to A415 formed by the main reference point, high-luminance point P4, and the high-luminance points P5 to P15. The linear section extraction unit 332 then calculates the difference between angles A45 to A415 and the linear section angles. Here, it is assumed that the differences between angles A45 to A411 and the linear section angles do not exceed the allowable value, and the differences between angles A412 to A415 and the linear section angles exceed the allowable value. Therefore, the linear section extraction unit 332 determines that high-luminance points P12 to P15 are curved surface high-luminance points. The linear section extraction unit 332 extracts high-luminance points P12 to P15 as curved surface high-luminance points. According to the method for extracting curved surface high-luminance points shown in Figure 8, curved surface high-luminance points can be accurately extracted.

[0034] As described above, the linear section extraction unit 332 extracts the range of high-luminance points P4 to P11 as a linear section, excluding the curved surface high-luminance points P12 to P15 from the high-luminance points P4 to P15 which are workpiece high-luminance points. Figure 9 shows the linear section extracted by the linear section extraction unit 332. In Figure 9, in the range of high-luminance points P4 to P11, not only the lines where high-luminance points P4 to P11 are located are shown, but also lines from which peak luminance has not been extracted. Here again, the number of lines is reduced compared to the actual number.

[0035] Even if the line laser beam is irradiated so as to span the upper end of the die Td and the sheet metal W, the linear portion extraction unit 332 excludes the die's high-brightness points from among the high-brightness points P1 to P15, thus enabling the extraction of linear portions from the workpiece's high-brightness points.

[0036] As shown in Figure 10, the linear all-pixel extraction unit 333 extracts all high-brightness points included in the linear section by extracting pixels with peak brightness in all lines that have not had pixels with peak brightness in the range of high-brightness points P4 to P11 extracted. As shown in Figure 11, the linear approximation unit 334 generates a linear line Ls by linearly approximating all high-brightness points included in the linear section shown in Figure 10, for example, using the least squares method. As shown in Figure 12, the linear angle calculation unit 335 calculates the image angle φ of the linear line Ls with respect to the horizontal direction.

[0037] Instead of generating a straight line Ls based on all the high-luminance points included in the straight line section shown in Figure 10, the straight line approximation section 334 may generate a straight line Ls by linearly approximating the high-luminance points P4 to P15 shown in Figure 9 using the least squares method. Providing a straight line all-pixel extraction section 333 is not essential. However, it is preferable to provide a straight line all-pixel extraction section 333 because generating a straight line Ls based on all the high-luminance points included in the straight line section allows for the generation of a more accurate straight line Ls.

[0038] Returning to Figure 3, the image angle φ of the straight line Ls calculated by the image angle calculation unit 33 of the angle sensors 30F and 30R is transmitted to the bending angle conversion unit 22 of the angle sensor control device 20. The bending angle conversion unit 22 converts the two image angles φ calculated by the image angle calculation unit 33 of the angle sensors 30F and 30R into the bending angle θ of the sheet metal W shown in Figure 2 and transmits it to the NC device 10. The NC device 10 compares the target bending angle with the actual bending angle θ of the sheet metal W bent to the target bending angle. Depending on the comparison result, the NC device 10 can control the press brake body 101 to bend the sheet metal W even closer to the target bending angle. Furthermore, the NC device 10 can control the press brake body 101 to bend the sheet metal W even closer to the target bending angle during subsequent bending processes.

[0039] As described above, the bending angle measuring device and bending angle measuring method according to one or more embodiments calculate the image angle φ based on the high-brightness points of the straight section of the workpiece, excluding the curved surface high-brightness points, and convert the image angle φ into the bending angle θ of the sheet metal W. Therefore, according to the bending angle measuring device and bending angle measuring method according to one or more embodiments, the bending angle θ of the sheet metal W can be accurately measured even if a part of the surface of the front flange Wf or rear flange Wr irradiated with line laser light is curved.

[0040] Incidentally, the method by which the straight-line portion extraction unit 332 extracts a reference point (this reference point) of the work high-brightness points from among a plurality of high-brightness points obtained by sampling a line image included in the captured image by the camera 35 is not limited to the method described in FIGS. 7A to 7D. The straight-line portion extraction unit 332 may extract this reference point by the method shown in FIG. 13.

[0041] As shown in FIG. 13, the straight-line portion extraction unit 332, for example, uses the high-brightness point P1 located at the bottommost position within the frame F as a provisional reference point, and calculates an angle A12 formed by the high-brightness point P1 and the high-brightness point P2 located one position above it. Next, the straight-line portion extraction unit 332 calculates an angle A13 formed by the high-brightness point P1 and the even higher high-brightness point P3. Since the difference between the angle A12 and the angle A13 is within the allowable value, the straight-line portion extraction unit 332 determines that the high-brightness point P3 is not the reference point of the work high-brightness points. The allowable value here does not have to be the same value as the allowable value used in the method described in FIGS. 7A to 7D.

[0042] Further, the straight-line portion extraction unit 332 calculates an angle A14 formed by the high-brightness point P1 and the high-brightness point P4. Since the difference between the angle A12 and the angle A14 exceeds the allowable value, the straight-line portion extraction unit 332 determines that the high-brightness point P4 and the high-brightness points P5 to P15 existing above it are work high-brightness points, and sets the high-brightness point P4 as the reference point.

[0043] The method for extracting the reference point of the work high-brightness points shown in FIG. 13 can be used when the line laser light is also irradiated on the upper end portion of the die Td, and the high-brightness points obtained by sampling the line image included in the captured image by the camera 35 include the die high-brightness points. When the line laser light is not irradiated on the upper end portion of the die Td and is only irradiated on the front flange Wf and the rear flange Wr, the method described in FIGS. 7A to 7D may be used.

[0044] When the straight-line portion extraction unit 332 uses the method shown in FIG. 13, since the straight-line portion angle is not used, it is not necessary for the NC device 10 to transmit the target bending angle to the angle sensor control device 20, and it is not necessary for the angle sensor control device 20 to transmit the straight-line portion angle to the image angle calculation unit 33.

[0045] Furthermore, the method by which the linear section extraction unit 332 extracts curved surface high-brightness points from the workpiece high-brightness points is not limited to the method described in Figure 8. The linear section extraction unit 332 calculates the difference between angle A45 and angle A46, the difference between angle A45 and angle A47, the difference between angle A45 and angle A48, and so on, between angle A45 and angles A46 to A415. The high-brightness point at an angle where the difference exceeds the allowable value, that is, the high-brightness point where the angle has changed beyond the allowable value, is the first high-brightness point of the curved surface high-brightness points. The linear section extraction unit 332 determines that high-brightness points P12 and beyond, which are high-brightness points at an angle where the difference exceeds the allowable value, are curved surface high-brightness points. The allowable value here does not have to be the same value as the allowable value used in the method described in Figure 8.

[0046] If the linear section extraction unit 332 uses a method to extract the first high-brightness point of the curved surface high-brightness points according to whether or not the angle changes beyond a tolerance value, the linear section angle is not used. Therefore, the NC device 10 does not need to transmit the target bending angle to the angle sensor control device 20, and the angle sensor control device 20 does not need to transmit the linear section angle to the image angle calculation unit 33.

[0047] The operation of the bending angle measuring device according to one or more embodiments, and the bending angle measuring method according to one or more embodiments, will be further explained using the flowchart shown in Figure 14. In Figure 14, when processing starts due to power being turned on to the press brake 100, the angle sensor control device 20 determines in step S1 whether or not a bending angle measurement request has been made from the NC device 10. If no bending angle measurement request has been made from the NC device 10 (NO), the angle sensor control device 20 repeats the process in step S1.

[0048] If a bending angle measurement request is made from the NC device 10 in step S1 (YES), the angle sensor control device 20 instructs the angle sensor 30 to irradiate and capture an image of line laser light in step S2. The angle sensor 30 irradiates the sheet metal W with line laser light and captures the reflected light in step S3. The image angle calculation unit 33 of the angle sensor 30 samples the line image included in the captured image in step S4. The image angle calculation unit 33 sets the selected high-brightness point at the workpiece high-brightness point as the reference point in step S5. The image angle calculation unit 33 may set the lowest high-brightness point or a high-brightness point in its vicinity at the workpiece high-brightness point as the reference point.

[0049] The image angle calculation unit 33 excludes the curved surface high-brightness points from the workpiece high-brightness points and extracts the straight line portion in step S6. The image angle calculation unit 33 extracts all the high-brightness points included in the straight line portion in step S7. The image angle calculation unit 33 linearly approximates all the high-brightness points in step S8. The image angle calculation unit 33 calculates the image angle of the linearly approximated straight line in step S9. The image angle calculation unit 33 transmits the image angle to the angle sensor control device 20. The bending angle conversion unit 22 converts the image angles obtained by the two angle sensors 30F and 30R into the bending angle of the sheet metal W in step S10. The angle sensor control device 20 transmits the bending angle to the NC device 10 in step S11.

[0050] The angle sensor control device 20 determines whether to end the operation of the bending angle measuring device by cutting off the power of the press brake 100 etc. in step S12. If the operation is not ended (NO), the bending angle measuring device repeats the processing after step S1. If the operation is ended (YES), the bending angle measuring device ends the processing.

[0051] In the example configuration of the bending angle measuring device shown in Figure 3, an image angle calculation unit 33 is provided on the sensor substrate 31 within the angle sensor 30. The image angle calculation unit 33 may also be provided within the angle sensor control device 20. Alternatively, the NC device 10 may have the same functions as the angle sensor control device 20, or the NC device 10 may have the same functions as the angle sensor control device 20 and the image angle calculation unit 33. The NC device 10 may also have the function of the operation instruction unit 32.

[0052] The present invention is not limited to the one or more embodiments described above, and can be modified in various ways without departing from the spirit of the invention.

[0053] This application claims priority based on Japanese Patent Application No. 2024-174352, filed with the Japan Patent Office on 3 October 2024, the full disclosure of which is incorporated herein by reference.

Claims

1. A bending angle measuring device comprising: a laser beam irradiation unit that irradiates a linear laser beam onto a first flange on the front side and a second flange on the rear side of a punch and a die in a workpiece that has been bent to a target bending angle by being sandwiched between a punch and a die; a camera that photographs the reflected light of the laser beam irradiated onto the first and second flanges; an image angle calculation unit that extracts a range of high-brightness points from a plurality of high-brightness points sampled from the line image of the reflected light contained in the image captured by the camera, excluding high-brightness points irradiated onto a region where the first or second flange is a curved surface, and calculates a linear image angle of a straight line approximated by at least the sampled high-brightness points contained in the linear section; and a bending angle conversion unit that converts the image angle into the bending angle of the workpiece.

2. The bending angle measuring device according to claim 1, wherein the image angle calculation unit extracts all high-luminance points included in the straight line, including high-luminance points that have not been sampled, and calculates the image angle of a straight line obtained by linearly approximating all high-luminance points included in the straight line.

3. The bending angle measuring device according to claim 1 or 2, wherein the laser light irradiation unit irradiates the first and second flanges so that the laser light is also irradiated onto the upper end of the die, and the image angle calculation unit extracts the straight section from the high-brightness points based on the reflected light of the laser light irradiated onto the first and second flanges, by excluding the high-brightness points based on the reflected light of the laser light irradiated onto the die from among the plurality of high-brightness points sampled from the line image included in the captured image.

4. The bending angle measuring device according to any one of claims 1 to 3, wherein the image angle calculation unit uses the lowest high-brightness point or a high-brightness point in its vicinity among the high-brightness points based on the reflected light of the laser light irradiated onto the first and second flanges as a reference point, calculates the angle between the reference point and each high-brightness point located above the reference point, and uses the principle angle of the line image due to the reflected light included in the captured image taken by the camera of the reflected light of the laser light irradiated onto the first and second flanges of the workpiece bent to the target bending angle as the straight-line section angle, and excludes the range of high-brightness points in which the difference between the angle between the reference point and each high-brightness point and the straight-line section angle exceeds an allowable value as high-brightness points irradiated onto a region where the first or second flange is a curved surface.

5. A bending angle measurement method comprising: irradiating a first flange on the front side and a second flange on the rear side of a punch and a die, which are bent to a target bending angle by being sandwiched between a punch and a die; capturing the reflected light of the laser beam irradiated onto the first and second flanges with a camera; sampling the line image of the reflected light contained in the image captured by the camera to obtain a plurality of high-brightness points; extracting high-brightness points from the plurality of high-brightness points, excluding those irradiated onto a region where the first or second flange is a curved surface, as a straight line; generating a straight line by linearly approximating at least the high-brightness points contained in the straight line; calculating the image angle of the straight line; and converting the image angle into the bending angle of the workpiece.

6. The bending angle measurement method according to claim 5, which involves extracting all high-luminance points included in the straight section, including high-luminance points that have not been sampled, and calculating the image angle of a straight line obtained by linearly approximating all high-luminance points included in the straight section.

7. The bending angle measurement method according to claim 5 or 6, wherein the laser light is irradiated onto the first and second flanges so as to irradiate the upper end of the die, and the linear portion is extracted from the high-brightness points based on the reflected light of the laser light irradiated onto the die, by excluding the high-brightness points based on the reflected light of the laser light irradiated onto the die from the plurality of high-brightness points sampled from the line image included in the captured image.

8. A bending angle measurement method according to any one of claims 5 to 7, wherein the lowest high-brightness point or a high-brightness point in its vicinity among the high-brightness points based on the reflected light of the laser light irradiated onto the first and second flanges is used as a reference point, the angle between the reference point and each high-brightness point located above the reference point is calculated, the principle angle of the line image due to the reflected light included in the captured image taken by the camera of the reflected light of the laser light irradiated onto the first and second flanges of the workpiece bent to the target bending angle is defined as the straight-line section angle, and the range of high-brightness points in which the difference between the angle between the reference point and each high-brightness point and the straight-line section angle exceeds an allowable value is excluded as high-brightness points irradiated onto a region where the first or second flange is a curved surface.

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