JP2768208B2 - Screw defect inspection device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus for inspecting a defect of a screw, and more particularly to an apparatus for inspecting a screw defect capable of reliably detecting a defect such as a dent at a tip portion of the screw.

[0002]

2. Description of the Related Art Conventionally, it has been very important to detect a defect such as a dent of a screw in order to prevent a serious situation in which the screw does not enter a mating nut. As a method of detecting the screw defect, for example, a method of visually inspecting the entire circumference of the screw can be considered. However, since the defect is naturally overlooked, in recent years, various types of automatic detection of the screw defect have been performed. Has been proposed.

[0003] For example, there is known a device for inspecting a complete thread portion at the root side of a screw (having the same thread shape) by utilizing the periodicity of the screw. In this device,
As shown in FIG. 7A, light is irradiated from a specific direction to a screw portion to be inspected, which is to be inspected. The screw defect is detected by the change in the output signal caused by the disturbance of the reflected light. Specifically, a screw defect is detected based on a change in the state of an output signal caused by reflected light incident on the light receiving unit.

[0004]

However, with such an apparatus, it is not always possible to reliably detect defects in all parts of the screw. For example, in a complete screw portion having a regular pattern repetition shape, a screw defect can be detected even with a conventional device. In some cases, defects could not be reliably detected.

This is because, as shown in FIG. 7 (b), the reflected light is disturbed even in the chamfered portion at the screw tip as in the case of the defect of the completely threaded portion. for disturbance of the intake section and not determine a disturbance of the reflected light due to the defect of the screw, there is a problem that can not be detected in full defects screws.

In addition, in general, a defect such as a dent is likely to occur near the screw tip chamfered portion. Therefore, the fact that the defect of the screw tip chamfered portion cannot be completely detected becomes a more serious problem. I was SUMMARY OF THE INVENTION The present invention has been made to solve the above-described problems, and has as its object to provide a screw defect inspection apparatus capable of suitably detecting a defect in a chamfered portion of a screw tip.

[0007]

According to the first aspect of the present invention, as shown in FIG. 1, an image obtained by photographing a screw is input, and a defect of the screw is determined based on the image. In a screw defect inspection apparatus for detecting, an original image creating means M1 for creating an original image of the screw as image information, and an inversion of the original image created by the original image creating means M1 to form a negative screw shape. An inverted image creating means M2 for creating an image and the original image created by the original image creating means M1 are shifted by a predetermined pitch in the axial direction of the screw ,
A post-image creating means M3 for creating a post-image of the screw, and the post-image created by the post-image creating means M3 and the inverted image created by the inverted image creating means are superimposed on each other to reduce an interference portion between the two images. An image comparing unit M4 to be obtained and a screw defect detecting unit M5 for detecting a screw defect based on an interference portion between the two images obtained by the image comparing unit M4.
The gist is a screw defect inspection device characterized by comprising:

[0008]

According to the present invention described above, an original image of a screw obtained by photographing a screw is created as image information by the original image creating means M1. Then, the original image is inverted by the inverted image creating means M2 to create an inverted image having a screw negative shape , and the post-image creating means M3 shifts the original image by a predetermined pitch in the axial direction of the screw. After the image is created. Then, the image comparing unit M4 superimposes the post-image created by the post-image creating unit M3 and the inverted image created by the inverted image creating unit M2 to obtain an interference portion where the two images overlap, and obtains the screw defect detecting unit M5. Accordingly, a screw defect is detected based on the interference portion where the two images overlap. In other words, if the screw has a defect, the defect cannot be detected even if the original image of the screw and its inverted image are directly superimposed.
When the pitch is shifted, in the shifted image, only the defective portion of the screw protrudes from the original image. Therefore, an inverted image of the screw to be inspected is created in advance, and when the inverted image is compared with the image after shifting the pitch, if the screw has a defect, a portion that interferes (overlaps) with both images occurs. Therefore, if there is such an interference portion, it is determined that the screw is defective.

In other words, if the screw has a defect, the defect cannot be detected even if the original image of the screw and its inverted image are directly superimposed, but if the original image is shifted by, for example, one pitch, the image after the shift will have a defect of the screw. Only the part protrudes from the original image. Therefore, an inverted image of the screw to be inspected is created in advance, and the inverted image is compared with the image after shifting the pitch. When the screw has a defect, a portion that interferes (overlaps) with both images occurs. Therefore, if there is such an interference portion, it is determined that the screw is defective.

[0010]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 2 is a schematic configuration diagram showing the entire configuration of the screw defect inspection device of the present embodiment, and FIG. 3 is a block diagram showing the electrical configuration thereof.

As shown in FIG. 2, 1 is a screw to be inspected, 2 is a turntable that fixes and rotates the screw 1, 3 is a motor that drives the turntable 2, and 4 is a transmission that irradiates the screw 1 with light. Illumination device, 5 is an area camera that receives light from the transmission illumination device 4, 6 is a general-purpose image processing device that changes a signal from the area camera 5 into image data, and 7 is various types of image data processed by the general-purpose image processing device 6. A monitor 10 for displaying an image is an electronic control unit for controlling the entire apparatus.

The rotary table 2 has a screw 1 fixed at the center of rotation, and is driven by a motor 3 to rotate at a predetermined constant speed in the direction of arrow A. The transmission illumination device 4 uniformly irradiates light from the side surface of the screw 1. The area camera 5 includes a transmission illumination device 4 and a screw 1.
The light received from the transmission illumination device 4 and transmitted around the screw 1 is received, and a two-dimensional bright and dark silhouette image of the screw 1 is detected.

The general-purpose image processing device 6 is a device having a data processing function as a computer for processing image data and determining a defect of the screw 1. As shown in FIG. 5, an image signal input circuit 6b for inputting a signal from the CPU 5, image memories A and B for storing input image data, a RAMI 6c for storing a processing program and measured values, and determination data for determining a defect of the screw 1 ( RA for storing reference values (Pml, PtL)
It comprises an MII 6d, an input port 6e and an output port 6f for exchanging data with the electronic control unit 10, and a bus 6g for connecting them. In this device 6, the signal from the area camera 5 is changed to a binary image to create an original image of the screw 1, and after the original image is shifted by one pitch toward the screw root, the image and the original image are combined. An inverted image that has been inverted is created, and a NOR operation is performed between the subsequent image and the inverted image.

The electronic control unit 10 is a device for controlling the entire screw defect inspection apparatus, and is a well-known CPU 10.
a, RAM 10b, ROM 10c, input port 10d,
It comprises an output port 10e and a bus 10f connecting them. The input port 10d is connected to the output port 6f of the general-purpose image processing device 6, and receives a determination signal indicating the result of the general-purpose image processing device 6 determining whether the screw 1 is good or bad. On the other hand, the output port 10e is connected to the input port 6f of the general-purpose image processing device 6, and outputs a start signal for starting the processing of the general-purpose image processing device 6. The motor 3 is connected to the output port 10e via a motor drive circuit 18 to output a control signal for controlling the rotation speed of the motor 3 and the like, and further, the screw 1 is automatically selected. And a control signal is outputted.

Next, the operation of the screw inspection apparatus having the above-described configuration will be described with reference to FIGS. Figure 4
Is a flowchart showing processing of the entire apparatus, and shows processing performed by the general-purpose image processing apparatus 6 in steps 110 to 210. FIG. 5 is an explanatory diagram showing a method for detecting a created image and a defect.

First, in the state where light is emitted from the transmitted illumination device 4 to the screw 1 and the light is received by the area camera 5, at step 100 in FIG.
To output a control signal to rotate the screw 1 at a constant speed. In this embodiment, for example, control is performed so as to rotate 140 ° per second.

Next, at step 110, the first image input from the area camera 5 to the general-purpose image processing device 6 is performed while the screw 1 is rotating. In step 120, the general-purpose image processing device 6 binarizes the input image signal to create an original image, and stores the original image in the image memory B.
To memorize. FIG. 5A schematically shows an original image of a screw tip portion (having a dent) stored in the image memory B.

[0018] At step 130, the original image stored in the image memory B and tone reversal, to create the FIG. 5 (b) to indicate such reversed image (screw gauge pattern), the reverse image in the image memory A Remember. In step 140, the original image stored in the image memory B is shifted downward by one pitch (toward the root of the screw 1), and a post-image as shown in FIG. 5C is created. Store in the image memory.

In step 150, the inverted image stored in the image memory A and the image stored in the image memory B are superimposed as shown in FIG. As a result, the dent portion (defect portion) of the screw 1 is represented by the overlapping portion between the inverted image and the subsequent image. Specifically, an inter-image memory operation (A NOR B) is performed to extract an overlapping portion (that is, a defective portion), and the area of each defective portion is obtained.

[0020] That is, the reverse image obtained by inverting the silhouette of the screw 1 with defects such as dents, for the portion corresponding to the defect of the screw 1 is similar screw shape, the original image and reverse image in situ Although the defective portion cannot be extracted by superimposing (see FIG. 6), when the original image of the screw 1 is shifted downward by one pitch and then superimposed, the defective portion is shifted to a non-defective portion of the screw 1. Thus, the overlapping portion of the two images can be extracted as a defect of the screw 1.

In the following step 160, noise removal is performed to determine the defective portion, and in step 170, the extracted lump, which is the determined defective portion, is labeled. In step 180, the area PIX (1) of the first extracted lump and the area PIX of the second extracted
The area sum Pn with (2) is obtained. The value of the first area sum Pn thus obtained is stored in the RAM I6c or the like for each time together with data indicating the number of times.

In step 190, it is determined whether or not n = 11. If n = 11, the flow returns to step 110 to perform processing for obtaining the (next time) area sum Pn.
If it becomes 1, the routine proceeds to step 200. In the present embodiment, since the screw 1 is processed 11 times at 19 ° intervals while rotating the screw 1 at 210 ° for 1.5 seconds, the area sum Pn for 11 times is calculated.

In step 200, the maximum value Pm is obtained from the area sums Pn stored in the RAMI 6c, and the total value Pt obtained by integrating all (11 times) area sums Pn is obtained. In step 210, the maximum value Pm of the area sum Pn is set to the reference value Pml stored in the RAM II 6d.
If the maximum value Pm is equal to or greater than the reference value PmL, it is determined that the screw 1 has a defect such as a dent. Also, the area sum P
n is compared with the reference value PtL similarly stored in the RAM II 6d, and the total value Pt is
If tL or more, it is determined that a part of the screw 1 is unprocessed, and the process is temporarily terminated. Note that PmL <PtL.

Then, based on the determination, the screw selecting device 19 is driven to automatically select the defective screw 1 and the good screw 1. That is, the maximum value Pm of the area sum Pn
Is smaller than the reference value Pml, the defect is slight and there is no problem. If the total value Pt of the area sum Pn is equal to or more than the reference value PtL, it is determined that there is a defect over the entire circumference, and it is determined that the defect has not been processed.

As described above, in this embodiment, an original image is created, an inverted image thereof and an image shifted by one pitch are created, and the inverted image is compared with the succeeding image. The presence or absence of a defect is determined based on the size of. Therefore, there is a remarkable effect that a defect such as a dent of a screw can be detected accurately and quickly. In particular, the present embodiment has a feature that a defect in a chamfered portion of a screw tip where it is difficult to detect a defect such as a dent can be reliably detected.

Further, by performing image processing in this way, in principle, not only a dent but also the detection of the attachment of a foreign substance and the loss of a screw and the unprocessed part of a screw can be detected in principle. Further, in this embodiment, the state of protrusion due to a defect can be detected using the contour shape of the screw itself, instead of using reflected light as in the related art. Can be detected.

Furthermore, since the process of shifting and overlaying the own image on the image memory is performed, there is an advantage that there is almost no shift error when overlapping the images. In addition, in this embodiment, for example, image shift, normal NOR
General-purpose processing such as logical operation and image inversion can be used.
It has a feature that the configuration of a general image processing apparatus is simplified.

It should be noted that the present invention is not limited to the above-described embodiment, and can be carried out in various modes without departing from the gist of the present embodiment. For example, in the above-described embodiment, the shift is performed by one pitch, but may be shifted by two pitches or more.

The number of times of obtaining the area sum Pn can be arbitrarily set according to the required accuracy.

[0030]

As described above in detail, the screw defect inspection apparatus according to the present invention compares a rear image with a reverse image and detects a screw defect based on the interference state between the two images. Therefore,
The remarkable effect that not only the complete thread portion of the screw but also the defect of the chamfered portion of the screw tip where it is difficult to detect a defect such as a dent can be surely detected. In addition to the dents, it is possible to detect the attachment of foreign matter, the loss of screws, and the unprocessed part of screws.

Furthermore, the state of protrusion due to a defect can be detected by using the contour shape of the screw itself instead of using the reflected light as in the prior art, so that it is possible to detect in advance whether or not "the screw does not enter" with high accuracy. can do. In addition, since the process of shifting the own image on the image memory and superimposing the image is performed, there is an advantage that there is almost no deviation error when the images are superimposed. Since general-purpose processing such as NOR logical operation and image inversion can be used, there is an advantage that the configuration of a general image processing apparatus can be simplified.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram illustrating a basic configuration of the present invention.

FIG. 2 is a system configuration diagram illustrating a screw defect inspection device according to an embodiment.

FIG. 3 is a block diagram showing an electrical configuration of the embodiment.

FIG. 4 is a flowchart illustrating image processing and the like.

FIG. 5 is an explanatory view showing various images created.

FIG. 6 is an explanatory diagram showing a state in which an original image and a reverse image are combined.

FIG. 7 is an explanatory diagram showing a conventional technique.

[Explanation of symbols]

M1 ... Original image creation means M2 ... Reverse image creation means M3 ... Post-image creation means M4 ... Image comparison means M5 ... Screw defect inspection means 1 ... Screw 2 ... Rotary base 3 ... Motor 4 ... Transmission illumination device 5 ... Area camera 6 ... General-purpose image processing device 7 ... Monitor 10 ... Electronic control device

Continuation of the front page (58) Field surveyed (Int. Cl. ⁶ , DB name) G01B 11/00-11/30 G01B 21/00-21/30 G01N 21/84-21/91

Claims (1)

(57) [Claims] 1. A screw defect inspection apparatus for inputting an image of a screw and detecting a screw defect based on the image, comprising: an original image creating means for creating an original image of the screw as image information; Inverting the original image created by the image creating means to create an inverted image forming a negative shape of the screw, a reversed image creating means, and converting the original image created by the original image creating means to the screw
A post-image creating unit that creates a post-image of the screw, shifted by a predetermined pitch in the axial direction, and superimposes the post-image created by the post-image creating unit and the inverted image created by the inverted image creating unit. Image comparing means for obtaining an interference portion between the two images, and screw defect detecting means for detecting a screw defect based on the interference portion between the two images obtained by the image comparing means. Screw defect inspection device.