Apparatus and method for inspecting appearance of semi-split cylindrical workpiece

Abstract

To provide a visual inspection device and a visual inspection method for half split cylindrical workpiece capable of accurately and inexpensively inspecting appearance of an inner peripheral face of the half split cylindrical workpiece.SOLUTION: A visual inspection device 1 comprises: a chuck 2 for inspecting an inner peripheral face 14a of half split cylindrical workpiece 14, and gripping the workpiece 14; an area camera 4 for imaging the workpiece 14 gripped by the chuck 2 from a peripheral end face 14b side thereof, for measuring a posture of the workpiece 14; a robot 6 for rotating the workpiece 14 along a peripheral direction B thereof, through the chuck 2; and a line scan camera 8 for imaging the inner peripheral face 14a of the workpiece 14 following rotation of the workpiece 14 for scanning. The robot 6 calculates a position and an inclination of a rotary shaft P2 being a rotary center of the workpiece 14 and a rotary start position P1 of the workpiece 14, on the basis of the posture of the workpiece 14 measured by the area camera 4, then, during rotation of the workpiece 14, for keeping a focal distance D of the line scan camera 8 to the inner peripheral face 14a of the workpiece 14 constant, corrects the position and inclination of the rotary shaft P2 and the rotary start position P1 while rotating the workpiece 14.SELECTED DRAWING: Figure 2

Description

[Technical field]

[0001] The present invention relates to an appearance inspection device and an appearance inspection method for a semi-split cylindrical workpiece. [Background technology]

[0002] Patent document 1 discloses an appearance inspection device that is composed of a camera that captures an image of an inspection target portion of an inspection object, a lighting device that irradiates light to obtain an image of the inspection target portion, a robot that moves freely in three dimensions while holding a part of the object that is not the inspection target portion in its hand so as to position the inspection target portion of the object at the focal position of an optical system consisting of the camera and the lighting device, and an image processing device that determines the pass / fail of the inspection object based on image data obtained by image processing the image obtained by driving the camera and the lighting device. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 06-160066 Summary of the Invention [Problem to be solved by the invention]

[0004] Camshafts and crankshafts are known as engine parts for automobiles, construction machines, ships, etc. Half bearings are used as bearings for these shafts. The inner circumferential surface of the half bearing for engine parts affects the performance of the bearing, so it is necessary to perform a strict visual inspection. However, such half cylindrical workpieces have subtle differences in the radius and opening of the inner circumferential surface according to the required specifications, in other words, the radius of curvature of the inner circumferential surface may change slightly and gradually, so it is difficult to perform a highly accurate visual inspection when the inner circumferential surface is the inspection target.

[0005] In addition, when a semi-split cylindrical workpiece is held by hand, in other words by a chuck, since the inner peripheral surface is the object of inspection, it is necessary to hold the narrow peripheral end surfaces formed at the upper and lower ends of the workpiece in the cylinder height direction. Therefore, errors are likely to occur in the holding position of the workpiece, and the attitude of the held workpiece is likely to vary, which is also one of the factors that reduces the inspection accuracy of the workpiece.

[0006] The device described in Patent Document 1 does not take into account the unique circumstances related to the appearance inspection of such semi-split cylindrical workpieces, and therefore there is a risk that the accuracy of the appearance inspection of the semi-split cylindrical workpieces may decrease. In addition, if an attempt is made to improve the inspection accuracy without taking special consideration, for example, the table on which the workpiece is placed and the camera and lighting for capturing the image of the workpiece must be moved, which may result in a complex device configuration and high costs.

[0007] The present invention has been made in consideration of such problems, and aims to provide an appearance inspection device and an appearance inspection method for semi-split cylindrical workpieces, which are capable of performing appearance inspection of the inner surface of a semi-split cylindrical workpiece with high precision and at low cost. [Means for solving the problem]

[0008] In order to achieve the above object, a visual inspection device for a semi-cut cylindrical workpiece according to one embodiment is a visual inspection device for inspecting an inner peripheral surface of a semi-cut cylindrical workpiece, Peripheral end surface of The chuck that holds the workpiece and the workpiece held by the chuck are imaged from the peripheral edge side. By processing the acquired images The area camera measures the workpiece's posture, and the workpiece is moved around its circumference via the chuck. Around the axis of rotation Rotate At the same time, the workpiece is moved along four axes: the X-axis, Y-axis, Z-axis, and rotation axis. The system includes a robot and a line scan camera that captures and scans an inner peripheral surface of the workpiece as the workpiece rotates, and the robot determines, based on the posture of the workpiece measured by the area camera, The focal length of the line scan camera relative to the inner circumferential surface is a predetermined constant value. Workpiece rotation start position and 、 Work of The position and inclination of the rotation axis By processing the images captured by the area camera, The focal length of the line scan camera relative to the inner surface of the workpiece is calculated and kept constant while the workpiece is rotating. By moving the workpiece,The workpiece is rotated while correcting the rotation start position and the position and inclination of the rotation axis.

[0009] In addition, a method for visually inspecting a semi-cylindrical workpiece according to one embodiment is a method for visually inspecting a semi-cylindrical workpiece by rotating the inner peripheral surface of the semi-cylindrical workpiece around a rotation axis along its circumferential direction and moving the workpiece in four axes, namely, an X-axis, a Y-axis, a Z-axis, and a rotation axis, and the method includes a gripping step of gripping a peripheral end surface of the workpiece, and a gripping step of gripping the workpiece gripped in the gripping step. By area camera Photographed from the peripheral edge side By processing the acquired images a measuring step for measuring the posture of the workpiece; As the workpiece rotates, the inner surface of the workpiece is imaged and scanned by a line scan camera. Based on the posture of the workpiece measured in the measuring step, a measurement is performed on the inner peripheral surface of the workpiece. To The method includes a calculation process for calculating the rotation start position of the workpiece, at which the focal length of the scanning of the line scan camera relative to the workpiece becomes a predetermined constant value, and the position and inclination of the rotation axis of the workpiece, by processing the image captured by the area camera; a rotation process for moving the workpiece to the rotation start position calculated in the calculation process and rotating the workpiece around the rotation axis calculated in the calculation process; a scanning process for imaging and scanning the inner surface of the workpiece at the focal length as the workpiece rotates in the rotation process; and a control process for correcting the rotation start position and the position and inclination of the rotation axis by moving the workpiece so as to keep the focal length constant in the scanning process while the workpiece is rotating. Effect of the Invention

[0010] According to the visual inspection device and visual inspection method for a semi-circular cylindrical workpiece of the present invention, visual inspection of the inner surface of a semi-circular cylindrical workpiece can be performed with high accuracy and at low cost. [Brief description of the drawings]

[0011] [Figure 1] 1 is a perspective view of a visual inspection device for a semi-split cylindrical workpiece according to a first embodiment. FIG. [Diagram 2] 1A to 1C are plan views of the workpiece, the area camera, and the line scan camera according to the first embodiment as viewed from above, showing the scanning of the inner circumferential surface by the line scan camera in chronological order. [Diagram 3]4 is a flowchart for explaining a visual inspection method using a visual inspection device according to a first embodiment. [Figure 4] 13(a) to 13(f) are plan views according to the second embodiment, showing the workpiece, the line scan camera, and the second illumination from above, and are diagrams showing the scanning of the inner circumferential surface by the line scan camera in chronological order. [Diagram 5] 10 is a flowchart for explaining a visual inspection method using a visual inspection device according to a second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an appearance inspection device and an appearance inspection method for a semi-split cylindrical workpiece according to each embodiment will be described with reference to the drawings. First Embodiment 1 shows a perspective view of a visual inspection device for a semi-split cylindrical workpiece according to the first embodiment. The visual inspection device (hereinafter also simply referred to as the device) 1 includes a chuck 2, an area camera 4, a robot 6, a line scan camera 8, a first illuminator 10, and a second illuminator 12. The workpiece 14 to be inspected is formed in a semi-split cylindrical shape, and has an inner peripheral surface 14a and peripheral end surfaces 14b formed at the upper and lower ends of the workpiece 14 in the cylinder height direction A.

[0013] The chuck 2 is connected to the tip 6b of the arm 6a of the robot 6, and holds the workpiece 14 at its upper and lower peripheral end faces 14b without covering the inner peripheral face 14a. The upper and lower parts of the chuck 2 are formed with protrusions 2a that protrude toward the line scan camera 8 and the second illumination 12. The workpiece 14 is held by being sandwiched between the protrusions 2a. The area camera 4 is fixed and captures an image of the workpiece 14 held by the chuck 2 from the lower peripheral end face 14b side in the imaging direction indicated by the dashed arrow to measure the attitude of the workpiece 14 (tilt with respect to the vertical direction).

[0014] The robot 6 is a SCARA robot (horizontal articulated robot) capable of moving the tip 6b of the arm 6a on four axes, namely, the X-axis, the Y-axis, the Z-axis, and a rotation axis. The robot 6 includes a controller 16 that controls the operation of the tip 6b of the arm 6a, and rotates the workpiece 14 in its circumferential direction B via the chuck 2 according to a command from the controller 16.

[0015] The line scan camera 8 is fixed and captures and scans an inner peripheral surface 14a of the workpiece 14 along a scanning line indicated by a dashed line as the workpiece 14 rotates. The first illuminator 10 is fixed and illuminates the imaging direction of the area camera 4 as indicated by a dashed line. The second illuminator 12 is fixed and illuminates the imaging direction of the line scan camera 8 as indicated by a dashed line. Each protrusion 2a of the chuck 2 protrudes in a direction opposite to the illumination direction of the second illuminator 12. The area camera 4 and the line scan camera 8 are electrically connected to a controller 16.

[0016] 2(a) to 2(c) are plan views of the workpiece 14, the line scan camera 8, and the second lighting 12 as viewed from above, and show the scanning of the inner peripheral surface 14a by the line scan camera 8 in a time series. Note that the area camera 4, the first lighting 10, and the controller 16 are not shown in Fig. 2. The controller 16 calculates the rotation start position P1 of the workpiece 14 and the position and inclination of the rotation axis P2, which is the center of rotation of the workpiece 14, relative to the vertical direction, based on a measurement signal of the attitude of the workpiece 14 transmitted from the area camera 4.

[0017] The controller 16 controls the operation of the arm 6a to rotate the workpiece 14 about the center of the circle of curvature while correcting the rotation start position P1 and the position and inclination of the rotation axis P2 in accordance with changes in the radius of curvature of the inner surface 14a, so as to keep the focal length D of the line scan camera 8 relative to the inner surface 14a of the workpiece 14 constant while the workpiece 14 is rotating. In other words, the controller 16 controls the rotation of the workpiece.

[0018] 3 shows a flowchart for explaining a visual inspection method using the apparatus 1. When visual inspection is started, first, in step S1, the chuck 2 manually or automatically grips the workpiece 14 (gripping process). Next, in step S2, the area camera 4 captures an image of the workpiece 14 gripped in the gripping process from its peripheral end face 14b side to measure the attitude of the workpiece 14 (measurement process). In the measurement process, the first illumination 10 illuminates the imaging direction.

[0019] Next, in step S3, the controller 16 calculates the rotation start position P1 of the work 14 and the position and inclination of the rotation axis P2 which is the center of rotation of the work 14 based on the attitude of the work 14 measured in the measurement process (calculation process). The rotation start position P1 and the position and inclination of the rotation axis P2 are calculated so that the focal length D of the scan with respect to the inner peripheral surface 14a of the work 14 becomes a predetermined constant value.

[0020] Next, in step S4, the robot 6 operates the arm 6a to move the workpiece 14 to the rotation start position P1 calculated in the calculation process, as shown in FIG. 2(a), and starts rotating the workpiece 14 around the rotation axis P2 whose position and inclination are calculated in the calculation process, as shown in FIG. 2(b) (rotation process).

[0021] Next, in step S5, the line scan camera 8 captures and scans the inner peripheral surface 14a of the workpiece 14 while maintaining the focal length D as shown in Fig. 2(c) as the workpiece 14 rotates in the rotation process (scanning process). In the scanning process, the imaging direction is illuminated by the second illumination 12. Next, in step S6, the controller 16 corrects the rotation start position P1 and the position and inclination of the rotation axis P1 during the rotation of the workpiece 14 so as to keep the focal length D in the scanning process constant at the initial setting value described above (control process).

[0022] Then, in step S7, it is determined whether the scanning process has been completed, and if the scanning process has not been completed (No), steps S2 to S6 are repeatedly executed while performing the above-mentioned workpiece rotation control. On the other hand, if the scanning process has been completed (Yes), the appearance inspection is terminated.

[0023] As described above, according to the visual inspection device 1 and visual inspection method for the semi-split cylindrical workpiece 14 of this embodiment, the robot 6 performs the above-mentioned workpiece rotation control, so that visual inspection of the inner peripheral surface 14a of the semi-split cylindrical workpiece 14 can be performed with high accuracy and at low cost. More specifically, even if the radius of curvature of the inner peripheral surface 14a of the workpiece 14 changes and an error occurs in the gripping posture of the workpiece 14, the line scan camera 8 can reliably perform focused, highly accurate scanning.

[0024] Moreover, since the area camera 4, the line scan camera 8, the first lighting 10, and the second lighting 12 are fixed and it is only necessary to rotate the workpiece 14 by the robot 6, the configuration of the device 1 is simplified and the costs associated with the appearance inspection can be reduced. Furthermore, in the appearance inspection device 1 and the appearance inspection method of this embodiment, the workpiece 14 is gripped by the chuck 2, so that the present invention is not limited to metal workpieces 14 having magnetic gripping means, for example, and can be applied to the appearance inspection of workpieces 14 made of various materials.

[0025] <Second embodiment> Hereinafter, the visual inspection method according to the second embodiment will be described with reference to Fig. 4 and Fig. 5. Note that the description of the same configuration as in the first embodiment will be omitted, and the configuration different from the first embodiment will be mainly described. The visual inspection method of this embodiment uses the device 1 described in the first embodiment, and in addition to the respective steps described in the first embodiment, a grip switching step of switching the gripping position of the workpiece 14 is performed.

[0026] 4(a) to (f) are plan views of the workpiece 14, the line scan camera 8, and the second illumination 12 viewed from above, and show the scanning of the inner peripheral surface 14a by the line scan camera 8 in a time series. Note that the area camera 4, the first illumination 10, and the controller 16 are not shown in FIG. 4. FIG. 5 shows a flowchart for explaining the appearance inspection method according to this embodiment using the apparatus 1. When the appearance inspection is started, first, in step S11, the chuck 2 manually or automatically grips one end side of the workpiece 14 in the circumferential direction B (gripping process).

[0027] Next, in steps S12 to S16, because one end of the workpiece 14 is held by the chuck 2, the same measurement process, calculation process, rotation process, scanning process, and control process as steps S2 to S6 described in the first embodiment are performed on the inner surface 14a (region R1) on the other end of the workpiece 14, and the workpiece 14 rotates sequentially as shown in Figures 4(a) to (c).

[0028] Then, in step S17, it is determined whether the scanning process of the region R1 is completed, and if the scanning process of the region R1 is not completed (No), steps S12 to S16 are repeatedly executed while performing the workpiece rotation control. On the other hand, if the scanning process of the region R1 is completed (Yes), the process proceeds to step S18.

[0029] In step S18, as shown in Fig. 4(d), the gripping of one end side of the workpiece 14 in the circumferential direction B by the chuck 2 is switched manually or automatically. Specifically, the workpiece 14 is turned upside down, and the other end side of the workpiece 14 in the circumferential direction B is gripped again (gripping switching step). Next, in steps S19 to S23, since the other end side of the workpiece 14 is gripped by the chuck 2, the measuring step, calculating step, rotating step, scanning step, and controlling step similar to steps S12 to S16 are performed on the inner circumferential surface 14a (region R2) on the one end side of the workpiece 14, and the workpiece 14 rotates sequentially as shown in Figs. 4(e) to (f).

[0030] Then, in step S24, it is determined whether the scanning process of region R2 has been completed, and if the scanning process of region R2 has not been completed (No), steps S19 to S23 are repeatedly executed while performing workpiece rotation control. On the other hand, if the scanning process of region R2 has been completed (Yes), the appearance inspection is terminated.

[0031] As described above, according to the method for visual inspection of the semi-cut cylindrical workpiece 14 of this embodiment, the robot 6 controls the workpiece rotation, and thus visual inspection of the inner peripheral surface 14a of the semi-cut cylindrical workpiece 14 can be performed with high accuracy and at low cost, as in the first embodiment. In particular, in this embodiment, the gripping switching process is performed, and the inner peripheral surface 14a of the semi-cut cylindrical workpiece 14 can be reliably scanned over the entire surface without being affected by the shadow caused by the chuck 2 or the blind spot caused when the workpiece 14 is rotated. Therefore, visual inspection of the inner peripheral surface 14a of the semi-cut cylindrical workpiece 14 can be performed with even higher accuracy.

[0032] Specifically, protrusions 2a are formed on the upper and lower parts of the chuck 2, protruding toward the line scan camera 8 and the second illumination 12. A shadow is cast on the inner circumferential surface 14a directly below the upper protrusion 2a, which may reduce the accuracy of scanning by the line scan camera 8. Also, a situation is assumed in which one end side of the workpiece 14 in the circumferential direction B is gripped by the chuck 2, and the inner circumferential surface 14a on the other end side of the workpiece 14 is inspected.

[0033] At this time, for example, if the workpiece 14 has a relatively large radius of curvature on the inner peripheral surface 14a, when the workpiece 14 is rotated and approaches the end of the scanning position on the inner peripheral surface 14a, the scanning line of the line scan camera 8 may be blocked by one end of the gripped workpiece 14, resulting in a blind spot on the inner peripheral surface 14a that cannot be scanned. However, by performing the grip switching process, these problems do not occur.

[0034] This concludes the description of each embodiment, but the above-described embodiments are not limiting and various modifications can be made without departing from the spirit and scope of the invention. For example, the first and second illuminators 10 and 12 can perform the appearance inspection with higher accuracy by illuminating the imaging directions of the area camera 4 and the line scan camera 8, respectively. However, if the installation environment of the device 1 allows it, the configuration of the device 1 may not include the first and second illuminators 10 and 12.

[0035] In addition, in the grip switching process described in the second embodiment, the other end side of the workpiece 14 in the circumferential direction B may be gripped again without turning the workpiece 14 upside down. In this case, in Figs. 4(a) to (f), when a line extending in the imaging direction of the line scan camera 8 and passing through the rotation axis P2 is used as a reference, one set of the line scan camera 8 and the second illuminator 12 are provided at positions symmetrical to the left and right, and the scanning process is performed by each set. This prevents the workpiece 14 itself from blocking the illumination by the second illuminator 12 as the workpiece 14 rotates, making scanning impossible. Therefore, each area R1, R2 can be suitably scanned by each line scan camera 8 while being illuminated by each second illuminator 12.

[0036] Furthermore, the appearance inspection device 1 and the appearance inspection method described in each embodiment can also be applied to the appearance inspection of the outer circumferential surface of the workpiece 14. For example, a pair of line scan cameras 8 and a pair of second lights 12 are placed opposite each other at positions sandwiching the workpiece 14, and the distance D between the opposing line scan cameras 8 is set to a value obtained by adding the thickness of the workpiece 14 in the radial direction to twice the focal length D of the line scan cameras 8.

[0037] This makes it possible to simultaneously inspect the inner peripheral surface 14a and the outer peripheral surface of the workpiece 14. The positions of the line scan cameras 8 are not limited to directly facing positions, and may be non-directly facing positions. Even in this case, by applying the above-mentioned appearance inspection method, it is possible to simultaneously inspect the inner peripheral surface 14a and the outer peripheral surface of the workpiece 14 even if the angles of the scanning lines of the line scan cameras 8 and the focal lengths D of the cameras are different. [Explanation of symbols]

[0038] 1. Visual inspection equipment 2 Chuck 4. Area Camera 6. Robot 8 Line scan cameras 10 First Lighting 12 Second Lighting 14 Semi-split cylindrical workpiece (workpiece) 14a Inner surface 14b Peripheral end surface B Circumferential direction D Focal length P1 Rotation start position P2 Rotational Axis

Claims

1. A visual inspection device for inspecting an inner peripheral surface of a semi-split cylindrical workpiece, A chuck that grips a peripheral end surface of the workpiece; an area camera for measuring the posture of the workpiece by capturing an image of the workpiece gripped by the chuck from the peripheral end surface side and processing the captured image; a robot that rotates the workpiece around a rotation axis along a circumferential direction of the workpiece via the chuck and moves the workpiece in four axes, i.e., an X-axis, a Y-axis, a Z-axis, and the rotation axis; a line scan camera that captures and scans the inner peripheral surface of the workpiece as the workpiece rotates; Equipped with The robot calculates the rotation start position of the work, which is formed on the inner surface of the work and at which the focal length of the line scan camera's scanning with respect to the inner surface is a predetermined constant value, and the position and inclination of the rotation axis of the work, by processing the image acquired by the area camera based on the posture of the work measured by the area camera, and rotates the work while correcting the rotation start position and the position and inclination of the rotation axis by moving the work so that the focal length of the line scan camera with respect to the inner surface of the work is constant during rotation of the work.

2. A first illumination that illuminates an imaging direction of the area camera; A second illumination that illuminates the imaging direction of the line scan camera; The visual inspection device for a semi-split cylindrical workpiece according to claim 1 , further comprising:

3. A visual inspection method for inspecting an inner peripheral surface of a semi-cut cylindrical workpiece by rotating the inner peripheral surface of the semi-cut cylindrical workpiece around a rotation axis along a circumferential direction of the inner peripheral surface and moving the workpiece in four axes including an X axis, a Y axis, a Z axis, and the rotation axis, comprising: a gripping step of gripping a peripheral end surface of the workpiece; a measuring step of measuring the attitude of the workpiece by processing an image obtained by capturing an image of the workpiece gripped in the gripping step from the peripheral end surface side using an area camera; a calculation process in which the inner peripheral surface of the workpiece is imaged and scanned by a line scan camera as the workpiece rotates, and a rotation start position of the workpiece formed on the inner peripheral surface of the workpiece at which a focal length of the scanning of the line scan camera with respect to the inner peripheral surface becomes a predetermined constant value, and a position and inclination of the rotation axis of the workpiece are calculated by processing the image captured by the area camera based on the posture of the workpiece measured in the measurement process; a rotation step of moving the workpiece to the rotation start position calculated in the calculation step and rotating the workpiece around the rotation axis calculated in the calculation step; a scanning step of imaging and scanning the inner peripheral surface of the workpiece at the focal length in accordance with the rotation of the workpiece by the rotating step; a control step of correcting the rotation start position and the position and inclination of the rotation axis by moving the workpiece during the rotation of the workpiece so as to keep the focal length constant in the scanning step; The method for visually inspecting a semi-split cylindrical workpiece includes:

4. The method for visually inspecting a semi-split cylindrical workpiece according to claim 3 , wherein in the measuring step and the scanning step, light is illuminated in each imaging direction.

5. The gripping step further includes a gripping switching step of gripping one end side of the workpiece relative to the center in the circumferential direction, switching the gripping of the one end side of the workpiece in the circumferential direction, and gripping the other end side of the workpiece relative to the center in the circumferential direction, 5. The method for visual inspection of a semi-split cylindrical workpiece according to claim 3 or 4, wherein, when the one end side of the workpiece is gripped, the measuring process, the calculating process, the rotating process, the scanning process, and the controlling process are performed on the entire inner surface at the other end side of the workpiece, whereas, when the other end side of the workpiece is gripped after the grip switching process, the measuring process, the calculating process, the rotating process, the scanning process, and the controlling process are performed on the entire inner surface at the one end side of the workpiece.

Images