JP2017026441A - Article inspection method and device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an article inspection method, even when an attitude of an article is changed, bringing a surface, the image of which is intended to capture, into focus in the method of inspecting a minute article by capturing images thereof from a plurality of directions.SOLUTION: The article inspection method includes: a step of holding one principal surface of an article 90 as a holding surface by a holding device 11 fixed to a tip of a multi-joint robot arm 71; a first image-capturing step of capturing an image of a surface of the article at an opposite side of the holding surface, with a camera 74 to acquire a first image; and a second image-capturing step of rotating the holding device and sequentially capturing images of a lateral face of the article with the camera. In the second imaging step, a distance between the lateral face intended to capture and the camera is adjusted.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a method for inspecting an appearance by imaging a minute article from a plurality of directions and an apparatus therefor.

  In recent years, the use of minute parts has increased due to the downsizing of electronic devices and the like and the precision of various mechanical devices. In addition, in the case of precision parts, the entire surface of the article may be inspected. In order to inspect the appearance of the article from a plurality of directions, it is possible to use a method in which the article is held by some method and the posture of the article is changed by an articulated robot arm and an image is taken with a camera.

  For example, Patent Document 1 describes an inspection method in which a workpiece is held by a hand unit attached to a robot system and inspected by an inspection camera while changing a plurality of workpiece postures.

JP 2012-223840 A

  However, in an inspection method in which an image is captured with a camera while changing the posture of the article, the surface to be imaged may not be in focus when the posture of the article is changed. In a camera used for inspecting a minute article, such a phenomenon is likely to occur because the focus range is narrow and the autofocus function is not so wide. Even when focusing is possible by the autofocus function, if the number of images taken for one article increases, the time required for focusing increases, so a decrease in inspection speed cannot be ignored.

  The present invention has been made in consideration of the above, and in a method of holding a minute article and imaging and inspecting from a plurality of directions while changing the posture, it is desired to take an image even when the posture of the article is changed. An object of the present invention is to provide an article inspection method capable of focusing on a surface. Another object of the present invention is to provide an article inspection apparatus capable of performing such an inspection method.

  In response to the above problems, the method for inspecting an article of the present invention includes a step of holding one main surface of an article as a holding surface by a holding device fixed to the tip of an articulated robot arm, and a side opposite to the holding surface of the article A first imaging step of acquiring a first image by imaging the surface of the article with a camera, and a second imaging step of sequentially imaging the side surfaces of the article with the camera by rotating the holding device. 2 In the imaging step, the distance between the side surface to be imaged and the camera is adjusted.

  Here, the main surface refers to a surface having a large area among the surfaces constituting the outer surface of the article. Further, the side surface means a surface other than the holding surface of the article and the opposite surface. By this method, when the side surface of the article is imaged in the second imaging step, the surface to be imaged can be focused, and high-precision appearance inspection can be performed.

  Preferably, in the second step, the distance between the side surface to be imaged and the camera is adjusted to a required distance corresponding to each side surface.

  Preferably, the position of the camera is fixed, and the distance between the side surface to be imaged and the camera is adjusted by the operation of the articulated robot arm. This eliminates the need to provide a separate mechanism for moving the camera for focusing, thereby reducing the manufacturing cost of the inspection apparatus.

  Preferably, on the basis of the first image obtained in the first imaging step, the distance between the side surface to be imaged in the second imaging step and the camera is adjusted. More preferably, the external shape and orientation of the article are recognized from the first image, and the distance between the side surface to be imaged in the second imaging step and the camera is adjusted based on the recognized external shape and orientation. The Thus, based on the first image, it is possible to obtain the position of the article in focus on the side imaged in the second imaging step at the same time as performing the appearance inspection of the surface opposite to the holding surface. The inspection time can be shortened.

  More preferably, the recognition of the outer shape and the orientation includes a step of acquiring an outer peripheral line of the article in the first image, a step of separating the outer peripheral line into a linear part and a corner part from a change amount of the outer peripheral line, The step of calculating the angle and the distance from the holding center of the article for each of the straight portion and the corner portion is realized. Here, the holding center of the article means a place where the central axis of the holding device is located in the first image, and becomes a rotation center when the holding device is rotated by the operation of the articulated robot arm. In this way, data necessary for focusing at the time of side surface imaging can be calculated from the first image.

  Preferably, the holding device is formed small so as not to protrude from the outline of the article in the first imaging step and to be reflected in the first image. Since there is no reflection of the holding device, it is possible to omit extra image processing for erasing the holding device from the image when extracting the outer peripheral line of the article from the first image.

  Preferably, the holding device is directly or indirectly fixed to the movable rod, a sleeve made of a non-magnetic material, a linear actuator in which a movable rod that linearly moves in the axial direction of the sleeve, and the movable rod; A magnet unit housed in the sleeve. The magnet unit is configured by one permanent magnet or a combination of a plurality of magnetic members including at least one permanent magnet, the front end surface is the first magnetic pole, and the rear end surface is the second magnetic pole. .

  Here, the front means a direction in which the article to be held is viewed from the holding device, and the rear means the opposite direction. The magnetic member is a member made of a magnetic material, and the magnetic material is a concept including a permanent magnet and a soft magnetic material. The first magnetic pole is an N pole or an S pole, and the second magnetic pole is an S pole or an N pole opposite to the first magnetic pole. Such a holding device is suitable for adsorbing and moving a minute article and can be reduced in size, and is particularly suitable for the appearance inspection of the present invention.

  Preferably, in the first imaging step and / or the second imaging step, the article is illuminated by low angle illumination. Here, the low angle illumination is illumination that irradiates light from a low angle with respect to the surface to be inspected. By using the low-angle illumination, scratches on the surface of the article are easily noticeable, and defects can be easily found. In addition, by using low-angle illumination, a clearer peripheral line can be obtained in the first image.

  The article inspection apparatus according to the present invention includes a holding apparatus that holds an article, an articulated robot arm that moves the article held by the holding apparatus to an imaging position, the holding apparatus being fixed to a distal end, and the imaging position. It is obtained by illuminating means for projecting on a certain article, and a camera for imaging the article projected by the illuminating means, and further imaging the surface opposite to the surface on which the article is held. And an arithmetic unit for instructing the articulated robot arm about the orientation and position of the article when the side of the article is imaged.

  With this configuration, when the side surface of the article is imaged, the surface to be imaged can be focused, and a high-precision appearance inspection can be performed.

  According to the visual inspection method or apparatus for an article of the present invention, when an image is taken with a camera while changing the attitude of the article with an articulated robot arm, the surface to be imaged is clearly focused even when the attitude of the article is changed. Can be matched. As a result, a more accurate appearance inspection can be performed automatically.

It is a figure showing the whole article inspection device composition of one embodiment of the present invention. It is a figure which shows the example of the articles | goods used as the object of the inspection method of this invention. It is a figure which shows the structure of the holding | maintenance apparatus of one Embodiment of this invention. It is a figure which shows the imaging part of the test | inspection apparatus of one Embodiment of this invention, and is a figure which shows a 2nd imaging process. It is process drawing of the inspection method of one Embodiment of this invention. It is a figure which shows a 1st imaging process. It is a figure for demonstrating the recognition method of an article | item shape. It is a figure which shows three external dimensions of articles | goods. It is a figure which shows the 1st imaging process with respect to the goods of another shape. It is a figure which shows the 1st imaging process (A) and 2nd imaging process (B) with respect to articles | goods of another shape. It is a figure for demonstrating the shape recognition method of the articles | goods of another shape. It is a figure which shows the modification of a structure of a magnet unit. It is a figure for demonstrating the positioning mechanism of the articles | goods in which the through hole was formed. It is a figure which shows operation | movement of the holding | maintenance apparatus of one Embodiment of this invention. It is a figure which shows the relationship between the outline of articles | goods, and the magnitude | size of a sleeve.

  An embodiment of the article inspection method and apparatus of the present invention will be described below. First, the configuration of the inspection apparatus according to the present embodiment will be described with reference to FIGS.

  In FIG. 1, the inspection device 70 of the present embodiment includes an article holding device 11, an articulated robot arm 71, a low angle ring illumination 72, a high angle ring illumination 73, a camera 74, and a calculation unit 75. Inspection is performed by holding the article 90 with a holding device and taking images from a plurality of directions with a camera while changing the posture and position of the article by the operation of the articulated robot arm.

  FIG. 2 shows an example of an article to be inspected. The article 90 is in the form of a piece and has main surfaces 91 and 92, and a through hole 97 is formed in the thickness direction. In FIG. 2, the side surface 93 has four flat portions 94, and each has a ridge portion 95 between adjacent flat portions. Note that the article 90 is merely an example of an inspectable article, and does not limit the article targeted by the present invention.

  In FIG. 3, the holding device 11 of this embodiment includes a sleeve 30, an air cylinder 35, and a magnet unit 41. The sleeve has an opening 32 at the front (lower side in FIG. 3) end. In the air cylinder, a main body 36 is fixed to the sleeve via a flange 38, and a movable rod 37 is accommodated in the sleeve. The magnet unit is fixed to the tip of the movable rod of the air cylinder. When the air cylinder extends, the magnet unit moves forward, and the article can be adsorbed at the opening. Details of the holding device will be described later.

  In FIG. 1, the articulated robot arm 71 has a plurality of rotation axes, so that a complex movement similar to that of a human arm is possible. The robot arm moves the article 90 adsorbed and held at the tip of the holding device 11 to the imaging position in a required posture. The robot arm requires at least the number of joints that enables the posture of the article to be arbitrarily changed at the imaging position and allows the distance between the camera and the article to be adjusted while maintaining the posture.

  In FIG. 4, the imaging unit includes a low-angle ring illumination 72 and a high-angle ring illumination 73 serving as illumination means, and a camera 74. FIG. 4 shows a state in which the side surface 93 of the article 90 faces the camera.

  The low angle ring illumination 72 is a ring type low angle illumination. Low-angle illumination projects light from a low angle onto the surface of an article to be inspected. As a result, scratches on the surface of the article are easily noticeable, and defects can be easily found. Here, the low angle means that the angle from the inspection surface is small, and the incident angle θi to the inspection surface, that is, the angle from the normal line standing on the surface of the article is large. The larger the incident angle θi, the clearer the defects can be raised. Therefore, it is preferably 45 ° or more, more preferably 60 ° or more, and particularly preferably 70 ° or more. In order to illuminate the surface of the article uniformly with low angle ring illumination, it is necessary to make the distance between the illumination and the article sufficiently close. The distance between the low-angle ring illumination and the article is preferably 20 mm or less.

  The high angle ring illumination 73 is a ring type high angle illumination. High-angle illumination projects light from a high angle onto the surface of an article to be inspected. High-angle illumination is a concept that includes illumination that irradiates light substantially perpendicular to the surface to be inspected, and includes epi-illumination. The high-angle illumination of this embodiment irradiates light substantially perpendicularly to the surface of the article to be imaged. The high angle ring illumination is preferably a diffuse illumination. This is because the luminance unevenness of the irradiated surface can be suppressed by weakening the directivity of the light beam. Moreover, epi-illumination that irradiates light coaxially with the camera may be used as the high-angle ring illumination. The high angle ring illumination is not essential, but is preferably used in combination with the low angle ring illumination 72. This is because the inspection area becomes clear.

  The camera 74 images the surface of the article projected on the two lights 72 and 73 through the holes of the two ring lights. The type of camera is not particularly limited, and various commercially available inspection cameras can be used.

  When the high angle ring illumination 73 is used, it is preferable to use a color camera using illuminations of different colors that do not overlap the wavelength range for the low angle ring illumination 72 and the high angle ring illumination. For example, a low-angle ring illumination can be red and a high-angle ring illumination can be blue, and can be imaged with a color camera.

  In FIG. 1, the calculation unit 75 processes the obtained image and determines the presence or absence of defects such as scratches, chipping, and foreign matter adhesion. The calculation unit also recognizes the outer shape and orientation of the article from the image obtained by imaging the surface opposite to the holding surface of the article, and determines the posture and position of the article when the side surface of the article is subsequently imaged.

  Next, the article inspection method of this embodiment will be described. FIG. 5 shows an inspection process diagram.

  In many cases, articles are supplied in a state of being stacked on a pallet or the like so that the article is first held by a holding device and taken up from the pallet or the like. More specifically, while confirming the position of the article with the camera that is the eye of the articulated robot arm, the robot arm is operated so that the holding device faces one of the main surfaces of the article, and the holding device is placed on the article. The opening end (31 in FIG. 3) of the sleeve is brought into contact with the main surface (holding surface), and the air cylinder is extended to advance the magnet unit to be attracted to the article. The article is picked up from a pallet or the like while being held by being adsorbed to the holding device.

  Next, the articulated robot arm is operated to move the article to the imaging position with the surface opposite to the holding surface of the article (hereinafter sometimes simply referred to as “opposite surface”) facing the camera. And an opposite surface is imaged and a 1st image is obtained (1st imaging process). At this time, the opposite surface does not need to be strictly perpendicular to the camera axis, and it is sufficient that the entire opposite surface is within a focused range. In addition, the thickness of the article (distance between the holding surface and the opposite surface) may be registered in advance in order to focus the opposite surface 92 with certainty. FIG. 6 shows this first imaging step.

  In this embodiment, the low-angle ring illumination is red and the high-angle ring illumination is blue, and the first image is obtained by imaging with a color camera. In the first image, the surface of the opposite surface appears blue due to the reflection of light from the high angle ring illumination. As a result, the inspection area becomes clear, and if there are scratches, foreign objects, etc. in the blue area, the red area is reflected by the reflection of light from the low-angle ring illumination, so that the defect can be easily detected.

  Furthermore, the outer peripheral line on the opposite surface appears red in the first image due to the reflection of light from the low-angle ring illumination. Depending on the shape of the article, the outer peripheral line of the holding surface may appear in the first image, which will be described later. In the article of FIG. 2, the outer circumferential line on the opposite surface coincides with the outer circumferential line of the article. This outer peripheral line can be extracted by color separation to recognize (calculate) the outer shape and orientation of the article. FIG. 7A shows an example of the extracted outer peripheral line.

  The external shape and orientation of the article can be recognized as follows, for example. First, the outer circumferential line is classified into a straight line portion and a corner portion based on the amount of change. Specifically, in FIG. 7B, a portion with a small change in the inclination of the outer peripheral line is classified as a straight portion (94a to 94d), and a portion with a large change is classified as a corner portion (95a to 95d). Next, an approximate straight line is created for the straight line portion by the least square method, a perpendicular is drawn from the holding center O of the article to the approximate straight line, and the length and angle of the perpendicular are calculated. On the other hand, for the corner, the length and angle of the straight line connecting the holding center and the point having the longest distance from the holding center are calculated. Here, the holding center of the article means a place where the central axis of the holding device is present in the image, and becomes a rotation center when the holding device is rotated.

  The inspection method according to the present embodiment does not exclude the use of article design data such as CAD data in recognizing the outer shape and orientation of the article. For example, if the CAD data of the article is used, the orientation of the article can be recognized by comparing with the outer peripheral line extracted from the first image, and the distance between the side surface and the camera can be adjusted based on the CAD data. However, when there are a wide variety of articles to be inspected, it takes time to register a large amount of data for all the articles. As described above, if the outer shape and orientation of the article can be acquired from the first image, it is not necessary to register the CAD data, or at least a small part of the CAD data (for example, the thickness of the article) is used. Thus, it is possible to reliably focus on the side surface to be imaged in the subsequent second imaging step.

  Next, the robot arm is operated based on the outer shape and orientation of the article recognized from the first image, the posture of the article is adjusted, the side is directed to the camera, and the distance between the article and the camera is focused on the side. The image is adjusted (second imaging step). FIG. 4 shows this second imaging step.

  And from the acquired image, the presence or absence of defects, such as a flaw of a side surface and a foreign material, is determined. Even in the image obtained in the second imaging step, the inspection area becomes clear because the side surface appears blue due to the reflection of light from the high-angle ring illumination. The inspection area can be registered in advance as a method of clarifying the inspection area, but in that case, the area registered on the periphery of the inspection area due to slight inclination of the article or camera, etc. Deviation may occur in the area. In the present embodiment, such an inconvenience does not occur because the inspection region is shown in blue on the actually captured image.

  The second imaging step is repeated as necessary while rotating the holding device. For example, for the article shown in FIG. 7, the flat surface portion 94 a, the ridge portion 95 a, the flat surface portion 94 b, the ridge portion 95 b, the flat surface portion 94 c, the ridge portion 95 c, the flat surface portion 94 d, and the ridge portion 95 d are included. On the other hand, the entire side surface of the article can be inspected by repeating the second imaging step eight times.

  As a method of rotating the holding device, a rotation mechanism may be incorporated in the holding device itself, and preferably, the holding device is rotated by an operation of an articulated robot arm. If the holding device is rotated by the operation of the articulated robot arm, the holding device does not require a rotation mechanism, and the holding device can be made smaller.

  Next, after all the inspections are completed, the articulated robot arm is operated to release the article on a pallet or the like and stack it. In order to inspect the holding surface of the article, for example, after the second imaging step, the article is once placed on a table, turned over, and held again with the holding device holding the original opposite surface. Good.

  As described above, according to the article inspection method of the present embodiment, even when the side surface is inspected while changing the posture of the article, the side surface can be reliably focused. In contrast, when shifting from the first imaging step to the second imaging step, or from the second imaging step for one side surface to the second imaging step for the other side surface, the holding center is simply set at a certain position. There was a case that the focus could not be adjusted just by changing the direction. This phenomenon is particularly likely to occur when the article is flat or elongated. This is because in such an article, the distance between the holding center and the surface varies greatly depending on the attitude of the article. Therefore, depending on the shape of the article, the inspection may not be completely automated. According to the article inspection method of the present embodiment, it is possible to reliably focus on the surface to be inspected regardless of the shape of the article.

  The inspection method or apparatus of this embodiment is particularly useful for strips and elongated articles. FIG. 8 shows the external dimensions of the article. The three outer dimensions X, Y, and Z are sizes in directions orthogonal to each other. From the viewpoint that the effect of the inspection method or apparatus of the present embodiment can be remarkably obtained, the ratio of any two of X, Y and Z of the article is preferably 1.1 or more, more preferably 1. 5 or more.

  Here, some examples will be described for dealing with specially shaped articles. In FIGS. 9 and 10, the camera and illumination are omitted.

  As shown in FIG. 9, when the holding surface 91 and the opposite surface 92 of the article 90 are not parallel, in the first imaging step, when the holding surface is perpendicular to the camera axis and the opposite surface faces the camera, the entire opposite surface is formed. Focus may not be achieved. At this time, if the angle formed by the holding surface 91 and the opposite surface 92 is known in advance, the posture can be adjusted so that the opposite surface is perpendicular to the camera axis. If the angle between the holding surface and the opposite surface cannot be known in advance, the approximate size of the angle may be obtained by preliminarily imaging the side surface from one or more directions.

  As shown in FIG. 10, when the article 90 has a truncated pyramid shape or the like and the holding surface 91 and the opposite surface 92 are different in size, in the first imaging step, the outer peripheral line of the opposite surface and the holding surface becomes the first image. May appear. In that case, both outer peripheral lines may be extracted to recognize the shape, or only the outer peripheral line of the opposite surface or only the outer peripheral line of the holding surface may be extracted. For example, only the outer periphery of the opposite surface may be extracted to recognize its outer shape and orientation, and the article may be imaged from the side to determine the angle between the side surface and the opposite surface. Thereafter, the posture of the article can be adjusted so that the side surface 93 is substantially perpendicular to the axis of the camera.

  As shown in FIG. 11, when the outer peripheral line in the first image has no straight line part, the outer peripheral line can be divided into a plurality of corners. At this time, the number of parts to be divided can be determined so that the entire corner is within a focused range when each corner is imaged. In FIG. 11, the outer periphery which is a circumference is divided into eight corners.

  Next, the holding device of the above embodiment will be described in detail based on FIG. 3 and FIGS.

  In FIG. 3, the sleeve 30 is made of a nonmagnetic material. As the nonmagnetic material, plastic, copper, aluminum or the like can be used. Among these, it is preferable to use plastic. This is because when the open end 31 of the sleeve comes into contact with the article, the article is hardly damaged.

  Further, the sleeve opening end 31 may be provided with a non-slip portion in order to suppress the displacement of the article. The anti-slip portion can be formed, for example, by sticking an elastic sheet made of rubber or resin having a thickness of about 0.1 mm to 0.3 mm to the opening end 31.

  The shape of the sleeve 30 is not particularly limited, but is preferably a cylindrical shape. This is because, regardless of the direction of the adsorbed article, it is difficult to protrude from the outline of the article, and it is difficult to get in the way of imaging. In the first imaging step shown in FIG. 6, if the sleeve protrudes from the outline of the article and is reflected in the first image, it becomes an obstacle when extracting the outer peripheral line. Further, in the second imaging step shown in FIG. 4, it is not preferable that the sleeve protrudes from the outline of the article because illumination shadows are formed on the side surface to be inspected. In FIG. 15, when the cross section of the sleeve 30 is circular, the diameter is preferably smaller than the maximum inscribed circle 98 of the contour of the article 90. Since it can be used for many types of articles, the diameter of the sleeve of the holding device is preferably 50 mm or less, more preferably 30 mm or less, and particularly preferably 20 mm or less.

  In the second imaging step shown in FIG. 4, the length of the sleeve 30 is preferably longer than the radius of the low angle ring illumination 72. Considering that the radius of general low-angle ring illumination is about 50 to 100 mm, the length of the sleeve is preferably 50 mm or more, more preferably 75 mm or more, and particularly preferably 100 mm or more.

  Returning to FIG. 3, the air cylinder 35 has a main body 36 fixed to the sleeve 30 via a flange 38. As a method for fixing the air cylinder to the flange and a method for fixing the sleeve, a known method such as screwing can be used. Further, the air cylinder body may be directly fixed to the sleeve without using the flange. Since the main body 36 is fixed to the sleeve, when the air cylinder expands and contracts, the movable rod 37 accommodated in the sleeve can linearly move in the axial direction relative to the sleeve.

  The air cylinder 35 is a kind of linear actuator. A linear actuator is a device that converts various types of energy into linear motion. As the linear actuator, in addition to an air cylinder, a hydraulic cylinder, an electric cylinder, a linear motor, or a motor that converts a rotational motion of the motor into a linear motion by a motion conversion mechanism can be used. Among these, it is preferable to use an air cylinder because it can be miniaturized and accurate control is easy.

  The magnet unit 41 is fixed to the tip of the movable rod 37. Thereby, when the air cylinder 35 expands and contracts, the magnet unit is guided to the inner surface of the sleeve 30 and linearly moves in the axial direction of the sleeve with the linear movement of the movable rod.

  The magnet unit 41 is configured by one permanent magnet or a combination of a plurality of magnetic members including at least one permanent magnet. The front end surface 47 of the magnet unit is a first magnetic pole (for example, N pole), and the rear end surface 48 on the opposite side is a second magnetic pole (for example, S pole). By forming the magnetic pole so as to face the opening 32 in this way, the magnetic flux density emitted from the front end surface of the magnet unit is increased, and a strong attracting force is obtained.

  The magnet unit 41 consists of two members in this embodiment. The front member is a permanent magnet 51. The rear magnetic member 61 may be a permanent magnet or a soft magnetic member made of a soft magnetic material. As the soft magnetic material, various known materials such as iron having high magnetic permeability can be used. Preferably, the foremost member of the magnet unit is a permanent magnet. This is because a stronger adsorption force can be obtained.

  In addition, the structure of a magnet unit is not restricted to the thing of FIG. For example, as shown in FIG. 12A, the magnet unit 42 may be composed of a single permanent magnet 52. Further, for example, as shown in FIG. 12B, the magnet unit 43 may be arranged with a soft magnetic member 63 at the front and a permanent magnet 53 at the rear.

  As the permanent magnet 51, it is preferable to use a magnet having a strong magnetic force. This is because an article made of more various materials can be adsorbed. The permanent magnet is preferably a Nd—Fe—B based magnet (neodymium magnet). Or the magnetic flux density in the front end surface 47 of the magnet unit 41 is preferably 300 mT or more, more preferably 400 mT or more, and particularly preferably 500 mT or more regardless of the type of the permanent magnet. This makes it possible to adsorb articles made of austenitic stainless steel that is not adsorbed by general magnets and articles made of many alloys containing iron, cobalt, nickel, chromium, manganese, and the like as components. Moreover, a micro article | item can be conveyed at high speed by hold | maintaining strongly with a strong magnetic force. From the viewpoint of easy availability, the magnetic flux density of the permanent magnet is preferably 700 mT or less.

  A method of fixing the magnet unit 41 to the tip of the movable rod 37 of the air cylinder is not particularly limited, and a method of bonding using an adhesive, a mechanical method using a screw, or the like can be used.

  A method for joining members constituting the magnet unit 41 is not particularly limited. In FIG. 3, the front permanent magnet 51 is attracted to and coupled to the magnetic member 61 adjacent to the rear by a magnetic force. In order to employ this structure, it is necessary that the attracting force between the permanent magnet and the magnetic member be significantly larger than the attracting force between the magnet unit and the article. For example, if the permanent magnet is a Ne—Fe—B type magnet and the article does not reach a general magnet, the attractive force between the permanent magnet and the magnetic member is remarkably large, so this structure can be adopted. With this structure, the permanent magnet 51 can be replaced very easily.

  The size of the permanent magnet 51 is preferably larger in that a strong magnetic force can be obtained. On the other hand, in the holding device of the present embodiment for a minute article, the holding device itself is desirably small, and the outer diameter in a cross section perpendicular to the sleeve axis is preferably 40 mm or less, more preferably. 20 mm or less. In practice, the type and size of the magnet for obtaining the required attractive force will be determined according to the type of article and the content of handling, and the sleeve will be selected according to the outer shape of the magnet. The length of the permanent magnet in the sleeve axial direction is not particularly limited. The longer the magnet, the stronger the magnetic force, so an appropriate length can be selected as necessary.

  In the present embodiment, the permanent magnet 51 is annular. When there is a hole in the attracting surface of the article, this shape acts as a magnetic positioning means for the article when the foremost member of the magnet unit is annular or cylindrical. This will be described below.

  When the article is attracted to the magnet, a force is applied to change the position and orientation of the article so that the lines of magnetic force emitted from the magnet pass through the article as much as possible. Many small parts have holes formed for fixing. The tendency to change the position and orientation at the time of suction becomes particularly remarkable when a hole penetrating the article is formed on the suction surface of the article.

  FIG. 13A shows a plan view of the article 90 in which the hole 97 is formed. When such an article is attracted to a magnet without a hole, for example, a cylindrical magnet 50, the article moves at the moment of adsorption, and the position or orientation is likely to change (change from FIG. 13B to FIG. 13C). . Moreover, even if it adsorbs once, an article | item will move easily during conveyance, and an article | item will also move easily at the moment of releasing an article | item. This phenomenon can also occur when an annular or cylindrical magnet 51 having a hole 57 is used (change from FIG. 13D to FIG. 13E). However, once the magnet hole 57 is concentric with the article hole 97 and the magnet is brought close to the attracting surface and once attracted, the position and orientation of the article are stabilized (FIG. 13F). In the holding device of the present embodiment, the magnet unit 41 can be brought close to and adsorbed while pressing the article with the sleeve so that the hole of the permanent magnet 51 and the hole of the article are concentric. Goods do not move easily. In order to suppress the deviation of the article due to the high-speed conveyance, it is preferable to provide a non-slip portion at the sleeve opening end 31 as described above.

  Next, operation | movement of the holding | maintenance apparatus of this embodiment is demonstrated based on FIG.

  In FIG. 14A, the holding device 11 is opposed to the holding surface 91 which is one main surface of the article so that the hole 57 of the permanent magnet 51 and the hole 97 of the article 90 are concentric. At this time, the magnet unit is in a position retracted into the sleeve.

  Next, in FIG. 14B, the holding device is brought close to the article, and the open end 31 of the sleeve is brought into contact with the holding surface 91 of the article. When the holding device is operated by a robot arm or the like, an accurate operation can be performed by adjusting the posture / position of the holding device while checking the position of the article with a camera serving as an eye of the robot.

  Next, in FIG. 14C, the air cylinder is extended, and the movable rod 37 and the magnet unit 41 are advanced to be attracted to the article 90. At this time, since the magnet unit is brought closer while holding the article at the sleeve opening end, the article does not move at the moment of adsorption. Further, since the article is pressed not on the point but on the entire circumference of the opening end, the article does not rotate at the moment of adsorption. When the magnetic force is strong, a sufficient attracting force can be obtained at a position where the front end surface 47 of the magnet unit is slightly retracted from the opening end 31 of the sleeve. In that case, you may stop just before the front end surface of a magnet unit contacts the article | item 90. FIG. Such control is also possible because precise position feed can be performed by the air cylinder.

  Next, in FIG. 14D, the holding device can be moved while the article is held. Also at this time, it is preferable to keep the sleeve open end 31 in contact with the article. When the holding device is moved using a robot arm or the like, a large force may act on the article. By keeping the sleeve open end in contact with the article, it is possible to prevent positional deviation and change in direction (rotation in a plane perpendicular to the axis) of the article being conveyed. In particular, when the holding device is used in the appearance inspection according to the present embodiment, high-speed conveyance as much as possible is required in order to shorten the tact time. Therefore, the actual moving speed of the robot arm may reach 2500 mm / second and the acceleration may reach 2.5 G. Even in such a case, stable handling of an article becomes possible by using the holding device of the present embodiment.

  The operation of releasing the article by the holding device 11 is opposite to the above-described adsorption operation. First, an article is placed at a required position (FIG. 14C). Next, the magnet unit is retracted while keeping the sleeve open end in contact with the article (FIG. 14B). At this time, since the magnet unit is moved backward while the article is held at the sleeve opening end, the article is unlikely to move when the magnet unit is released. Then, after the magnet unit is completely retracted, the holding device is separated from the article to release the article (FIG. 14A).

  The reason why the holding device of this embodiment is suitable for the inspection method of this embodiment will be described again.

  As a holding device for a minute article, for example, a device that grips an article with a chuck such as a three-claw is also used. However, such a holding device is not preferable because the nail hides a part of the surface to be inspected when the article is imaged. In addition, as another micro article holding device, an apparatus for vacuum-sucking an article to a nozzle is also used. However, such a holding device cannot be used when there are irregularities such as grooves and protrusions on the adsorption surface of the article, or there are holes that penetrate the article, and the shape of the article that can be held is limited. There is.

  Further, according to the holding device of the present embodiment, the magnet is attracted while the sleeve is brought into contact with the article and the article is pressed, so that it is difficult for the article to move during the adsorption and to be displaced or changed in direction. . At this time, since the article is pressed by the open end of the circular sleeve, the article is less likely to rotate than when the pin is pressed at one point. Even after the article is attracted to the magnet unit, the article is not easily displaced or rotated during conveyance by maintaining the state where the sleeve open end is in contact with the article. When releasing the article, the magnet is detached while holding the article with the sleeve, so that the article hardly moves at the moment of separation. As a result, the article can be released to an accurate position.

  Furthermore, since the annular permanent magnet 51 is disposed on the front end surface of the magnet unit in the holding device of the present embodiment, a positioning effect can be obtained with respect to the article in which the hole is formed. That is, since the magnet is adsorbed while holding the article with the sleeve, the article does not move at the moment of adsorption, and the magnet unit can be adsorbed by concentrating the hole of the permanent magnet 51 and the hole of the article. When the two holes are concentric and the suction is completed, the position of the article is not likely to be shifted or the direction is changed during the conveyance. Even when the article is released, the article is difficult to move.

  The article inspection method and apparatus of the present invention are not limited to the above-described embodiment, and various modifications are possible within the scope of the technical idea.

  For example, in the above embodiment, different colors are used for the low angle illumination and the high angle illumination, but instead, the low angle illumination and the high angle illumination are sequentially turned on regardless of the colors of the low angle illumination and the high angle illumination. Thus, two images may be sequentially captured by one camera. Even in this case, by superimposing the two images, the same effect as in the case of using different color illumination for the low angle illumination and the high angle illumination can be obtained. Furthermore, when capturing two images sequentially, a monochrome camera can be used as the camera, and a higher definition image than a color camera can be obtained.

  The article inspection method and apparatus of the present invention can be used for various articles. Examples of such articles include micro magnets, bolts, nuts, carbide tips, tablets, cam parts, connector pins, and the like.

11 Article Holding Device 30 Sleeve 31 Sleeve Open End 32 Sleeve Open 35 Air Cylinder (Linear Actuator)
36 Air cylinder body 37 Air cylinder movable rod 38 Flange 41-43 Magnet unit 47 Front end surface of magnet unit 48 Rear end surface of magnet unit 51-53 Permanent magnet 57 Permanent magnet hole 61, 63 Magnetic member 70 Inspection device 71 Articulated Robot arm 72 Low-angle ring illumination θi Incident angle 73 High-angle ring illumination 74 Camera 75 Computing unit 90 Article 91 Main surface (holding surface) of article
92 Main surface (opposite surface)
93 Side of the article 94 Flat portion of the side, straight line of the outer peripheral line 95 Edge of the side, corner of the outer peripheral line 97 Hole of the article 98 Maximum inscribed circle of the outline of the article

Claims (10)

A step of holding one main surface of the article as a holding surface by a holding device fixed to the tip of the articulated robot arm;
A first imaging step of acquiring a first image by imaging a surface of the article opposite to the holding surface with a camera;
A second imaging step of rotating the holding device and sequentially imaging side surfaces of the article with the camera;
Adjusting the distance between the side surface to be imaged and the camera in the second imaging step;
Article inspection method. In the second step, the distance between the side surface to be imaged and the camera is adjusted to be a required distance corresponding to each side surface.
The article inspection method according to claim 1. The position of the camera is fixed, and the distance between the side surface to be imaged and the camera is adjusted by the operation of the articulated robot arm.
The article inspection method according to claim 1 or 2. Based on the first image obtained in the first imaging step, a distance between the side surface to be imaged in the second imaging step and the camera is adjusted.
The article inspection method according to any one of claims 1 to 3. The external shape and orientation of the article are recognized from the first image, and the distance between the side surface to be imaged in the second imaging step and the camera is adjusted based on the recognized external shape and orientation.
The article inspection method according to claim 4. Recognition of the outer shape and orientation is
Obtaining a peripheral line of the article in the first image;
Separating the outer peripheral line into a straight line part and a corner part from the amount of change of the outer peripheral line;
The step of calculating the angle and the distance from the holding center of the article for each of the straight portion and the corner portion is realized.
The article inspection method according to claim 5. The holding device is formed small enough to protrude from the outline of the article in the first imaging step and not appear in the first image.
The article inspection method according to any one of claims 1 to 6. The holding device is
A sleeve made of non-magnetic material;
A linear actuator in which a movable rod that linearly moves in the axial direction of the sleeve is inserted into the sleeve;
A magnet unit fixed directly or indirectly to the movable rod and housed in the sleeve;
The magnet unit is
It is constituted by a combination of a plurality of magnetic members including one permanent magnet or at least one permanent magnet,
The front end face is the first magnetic pole, and the rear end face is the second magnetic pole.
The article inspection method according to any one of claims 1 to 7. In the first imaging step and / or the second imaging step, the article is illuminated by low angle illumination.
The article inspection method according to any one of claims 1 to 8. A holding device for holding an article;
An articulated robot arm that is fixed to a tip of the holding device and moves the article held by the holding device to an imaging position;
Illumination means for projecting the article at the imaging position;
A camera that images the article projected by the illumination means;
An arithmetic unit for instructing the articulated robot arm of the orientation and position of the article at the time of imaging the side of the article based on an image obtained by imaging the surface opposite to the surface on which the article is held; Having an article inspection device.

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