Bending angle measuring device and bending angle measuring method

Abstract

The present invention provides a bending angle measuring device that can accurately measure the bending angle of a workpiece even if a portion of the surface of the workpiece irradiated with laser light is curved. [Solution] The laser diode 34 irradiates a linear laser beam onto the first flange on the front side and the second flange on the rear side of the punch and die of the workpiece that has been bent to a target bending angle. The camera 35 captures the reflected light of the laser beam irradiated onto the first and second flanges. The image angle calculation unit 33 extracts a range of high-brightness points from among a plurality of high-brightness points sampled from the linear image of the reflected light contained in the image captured by the camera 35, excluding the high-brightness points irradiated onto the region where the first or second flange is a curved surface, and calculates a linear image angle by linearly approximating the sampled high-brightness points that are included in at least the linear portion. The bending angle conversion unit 22 converts the image angle into the bending angle of the workpiece.

Description

Technical Field

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

Background Art

[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 disposed 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. The bending angle measuring device includes a contact type and a non-contact type, and Patent Document 1 describes a non-contact type bending angle measuring device.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Typically, a non-contact type bending angle measuring device irradiates a linear laser beam onto a workpiece, 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 irradiated with the laser beam is flat.

[0005] However, the ends of workpieces bent by the press brake may have burrs due to shearing. Burrs are rounded or concave shapes formed on the edges of the sheared surface of a workpiece. If the workpiece is a long, thin sheet, such as a 1mm thick plate, the ends of the workpiece may droop when bent by the press brake. Furthermore, the ends of the workpiece may have a rounded shape, sometimes referred to as an R-shape, intentionally formed on them. In such cases, a portion of the surface of the workpiece to which the laser beam is irradiated may be curved. If a portion of the surface of the workpiece to which the laser beam is irradiated is curved, errors may occur in the measurement angle, making it impossible to accurately measure the bending angle of the workpiece.

[0006] There is a need for a bending angle measuring device and method that can accurately measure the bending angle of a workpiece even if a portion of the surface of the workpiece being irradiated with laser light is curved. [Means for solving the problem]

[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 on 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 high-brightness points from the plurality of high-brightness points excluding those irradiated in a region where the first or second flange is a curved surface as a straight line portion, generating a straight line by linearly approximating at least the high-brightness points included in the straight line portion, calculating the image angle of the straight line, and converting the image angle into the bending angle of the workpiece. [Effects of the Invention]

[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. [Brief explanation of the drawing]

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

Embodiments for Carrying out the Invention

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

[0012] First, using FIG. 1, an overall configuration example of a press brake 100 equipped with a bending angle measuring device according to one or more embodiments and its schematic operation will be described. As shown in FIG. 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 portion excluding the NC device 10 and the bending angle measuring device described later will be referred to as the press brake main 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 move up and down by hydraulic cylinders 6L and 6R provided on the left and right. The hydraulic cylinders 6L and 6R constitute a table lifting mechanism. The table lifting mechanism may include actuators other than the hydraulic cylinders 6L and 6R. The table lifting mechanism may be configured by other components than the hydraulic cylinders 6L and 6R. The table lifting mechanism lowers the upper table 1 so as to approach the lower table 3 or raises it so as to be separated from the lower table 3.

[0014] The upper mold holder 2 is fitted with the upper mold, which is the punch Tp, and the lower mold holder 4 is fitted with the lower mold, which is the die Td. Figure 1 shows a modular type in which the upper mold 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 the punch Tp is attached are attached in the longitudinal direction of the lower end of the upper table 1. The intermediate plates are also upper mold 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 board 31, a laser diode 34, and a camera 35. The sensor board 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 board 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), as shown by the 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] Camera 35 captures the reflected light of the line laser beam irradiated onto the front flange Wf and the rear flange Wr from 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 and corresponds 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 lines, 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, 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 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 the 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 high-luminance point P2 as a provisional reference point and calculates the angle A23 between high-luminance point P2 and 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 high-luminance point P2 is a die high-luminance point. Similarly, in the angle A34 between 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 high-luminance point P3 is a die high-luminance point.

[0032] As shown in Figure 7D, the linear section extraction unit 332 uses high-brightness point P4 as a provisional reference point and calculates the angle A45 between high-brightness point P4 and 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 high-brightness point P4 is a workpiece high-brightness point. The linear section extraction unit 332 sets 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 high-brightness point P4, as the main reference point. The linear section extraction unit 332 determines that high-brightness point P4 and 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 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 of the workpiece. 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 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 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 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 operations.

[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] By the way, the method by which the linear section extraction unit 332 extracts the reference point (main reference point) of the workpiece high-brightness point from among multiple high-brightness points sampled from the line images included in the image captured by the camera 35 is not limited to the method described in Figures 7A to 7D. The linear section extraction unit 332 may also extract the main reference point by the method shown in Figure 13.

[0041] As shown in Figure 13, 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. Next, the linear section extraction unit 332 calculates the angle A13 between high-luminance point P1 and another high-luminance point P3 located further above it. Since the difference between angle A12 and angle A13 is within the allowable value, the linear section extraction unit 332 determines that high-luminance point P3 is not the actual reference point for the workpiece high-luminance points. The allowable value here does not have to be the same value as the allowable value used in the method described in Figures 7A to 7D.

[0042] Furthermore, the linear section extraction unit 332 calculates the angle A14 formed by high-luminance point P1 and high-luminance point P4. Since the difference between angle A12 and angle A14 exceeds the allowable value, the linear section extraction unit 332 determines that high-luminance point P4 and high-luminance points P5 to P15 above it are workpiece high-luminance points, and sets high-luminance point P4 as the main reference point.

[0043] The method for extracting the main reference point for the workpiece high-brightness point shown in Figure 13 can be used when the line laser beam is also irradiated to the upper end of the die Td, and the high-brightness point sampled from the line image included in the image captured by the camera 35 includes the die high-brightness point. If the line laser beam is not irradiated to the upper end of the die Td, but only to the front flange Wf and rear flange Wr, the method described in Figures 7A to 7D should be used.

[0044] When the linear section extraction unit 332 uses the method shown in Figure 13, the linear section angle is not used, so 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.

[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, such as when the power of the press brake 100 is turned on, 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 the NC device 10 requests measurement of the bending angle in step S1 (YES), the angle sensor control device 20 instructs the angle sensor 30 to irradiate and capture line laser light in step S2. In step S3, the angle sensor 30 irradiates the sheet metal W with line laser light and captures the reflected light. In step S4, the image angle calculation unit 33 of the angle sensor 30 samples the line image included in the captured image. In step S5, the image angle calculation unit 33 sets the selected high-brightness point in the workpiece high-brightness points as the reference point. The image angle calculation unit 33 may set the lowest high-brightness point in the workpiece high-brightness points or a high-brightness point in its vicinity as the reference point.

[0049] In step S6, the image angle calculation unit 33 extracts straight sections by excluding curved surface high-brightness points from the workpiece high-brightness points. In step S7, the image angle calculation unit 33 extracts all high-brightness points included in the straight sections. In step S8, the image angle calculation unit 33 approximates all high-brightness points with a straight line. In step S9, the image angle calculation unit 33 calculates the image angle of the straight-line approximated straight line. The image angle calculation unit 33 transmits the image angle to the angle sensor control device 20. In step S10, 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 S11, the angle sensor control device 20 transmits the bending angle to the NC device 10.

[0050] In step S12, the angle sensor control device 20 determines whether or not to terminate the operation of the bending angle measuring device by cutting off the power to the press brake 100, etc. If the operation is not terminated (NO), the bending angle measuring device repeats the processing from step S1 onwards. If the operation is terminated (YES), the bending angle measuring device terminates 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 same functions as the angle sensor control device 20 may be provided within the NC device 10, or the same functions as the angle sensor control device 20 and the image angle calculation unit 33 may be provided within the NC device 10. 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. [Explanation of Symbols]

[0053] 1 Upper table 2 Upper mold holder 3 Lower table 4. Lower mold holder 5L,5R side plate 6L, 6R Hydraulic Cylinders 7 Operation Pendant 8 Footswitches 10 NC device 20 Angle sensor control device 21. Straight section angle conversion section 22 Bending angle conversion section 30, 30F, 30R Angle Sensor 31 Sensor board 32 Operation instruction section 33 Image Angle Calculation Unit 34. Laser diode (laser light irradiation part) 35 Camera 40 Back Gauge 41 Back Gauge Carriage 42a, 42b Nose 100 Press Brake 101 Press brake body Td Die Tp Punch W Sheet metal (work) Wf Front flange (first flange) Wr Rear flange (second flange)

Claims

1. A laser beam irradiation unit that irradiates a linear laser beam onto the first flange on the front side and the second flange on the rear side of the punch and die of a workpiece that has been sandwiched between the punch and die and bent to a target bending angle, A camera for capturing the reflected light of the laser beam irradiated onto the first and second flanges, An image angle calculation unit extracts a range of high-luminance points from a plurality of high-luminance points sampled from the line images of reflected light contained in the image captured by the camera, excluding the high-luminance points that illuminated the region where the first or second flange is curved, and calculates the image angle of a straight line obtained by linearly approximating at least the sampled high-luminance points contained in the straight line. A bending angle conversion unit that converts the aforementioned image angle into the bending angle of the workpiece, A bending angle measuring device equipped with the following features.

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

4. The image angle calculation unit, 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 beam irradiated onto the first and second flanges is used as the reference point, and the angle between the reference point and each high-brightness point located above the reference point is calculated. The theoretical angle of the linear image formed by the reflected light, which is included in the captured image taken by the camera of the laser light irradiated onto the first and second flanges of the workpiece bent to the target bending angle, is defined as the linear section angle. The range of high-brightness points in which the difference between the angle between the reference point and each high-brightness point and the linear section angle exceeds the allowable value is excluded as high-brightness points irradiated onto the region where the first or second flange is curved. The bending angle measuring device according to claim 1 or 2.

5. A linear laser beam is irradiated onto the first flange on the front side and the second flange on the rear side of the punch and die of a workpiece that has been bent by being sandwiched between the punch and die. The reflected light of the laser beam irradiated onto the first and second flanges is captured by a camera. Multiple high-luminance points are obtained by sampling the line image of the reflected light contained in the image captured by the camera. Of the multiple high-luminosity points, the high-luminosity points that are irradiated to the region where the first or second flange is curved are excluded and extracted as straight-line portions. A straight line is generated by linearly approximating at least the high-luminance points included in the aforementioned straight section. The image angle of the aforementioned straight line is calculated, Convert the aforementioned image angle to the bending angle of the workpiece. Method for measuring bending angle.

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