KR20110084093A - Apparatus for inspecting screw thread - Google Patents

Abstract

PURPOSE: An apparatus for inspecting screw thread is provided to accurately detect uneven portions on screw thread by arranging image-pickup sensors in positions to receive only the lights reflected from the uneven portion of the screw thread surface. CONSTITUTION: An apparatus for inspecting screw thread comprises a light source(2a,2b) which partially or completely illuminates the outer surface of a screw being rotated, image-pickup sensors which receive the reflection lights from the screw, and an image processor which recognizes the shape of the screw thread based on the rotation information and the image information on the screw.

Description

Thread Inspection Device {APPARATUS FOR INSPECTING SCREW THREAD}

The present invention relates to a thread inspection device. In particular, it is related with the test | inspection apparatus which detects the unevenness | corrugation formed in the mountain of an external thread.

Spark plugs used in car engines and heating appliances have a screw structure for ease of replacement. Moreover, the screw structure is used also for the ball screw used for position adjustment of a stage. However, if there are irregularities such as a screw thread being crushed, the male screw and the female screw cannot be combined securely, or they cannot be removed even if they can be screwed together. For this reason, in these manufacturing processes, a shape test | inspection as to whether a screw thread is not crushed or an allowable range is performed in the manufacturing process is carried out.

As an apparatus for inspecting the shape of a thread, for example, Patent Document 1 discloses an apparatus for imaging the transmitted light obtained from the side on the opposite side by illuminating light from one side with respect to the thread. Radiated light is shielded from the part of a screw thread, becomes a silhouette, and detects the shape of a screw by detecting the transmitted light of the valley part. However, although such a device can detect a shape defect of a seedling, the defect may not be recognized depending on the degree of deformation.

6 shows a schematic structure for explaining the principle of a conventional inspection apparatus. (a)-(d) are the shapes of an inspection object, respectively, and (a1)-(d1) shows the structure in which the light source on the left side and the image sensor are arrange | positioned on the right side with an inspection object between them. (a2)-(d2) show the state which looked at the test object from the light source side. The inspection object is based on a triangular plate for convenience of explanation.

(a) shows the state in which a test object is normal. The light emitted from the light source is partially shielded from the inspection object, and the shape of the inspection object is recognized by the light that reaches the image sensor without being shielded.

(b) shows the state where the vertex of the inspection object is missing. In this case, since the emitted light from the light source is not shielded at the missing portion, the image sensor recognizes the shape shown in (b2). Thus, the shape defect can be detected by comparing with the normal pattern stored in advance.

(c) is also a state in which the test object is deformed similarly to (b), and shows the state in which the vertex of the test object is crushed and the burr is formed. Also in this case, the image sensor recognizes the burr as a light shielding part.

(d) shows the state in which the unevenness | corrugation was formed in the side part at the light source side of a test object. In this case, since the overall shape of the inspection object is the same as the normal pattern, the image sensor cannot detect the presence or absence of irregularities.

As described above, when the shape change occurs in the direction crossing the light path from the light source to the image sensor, the image sensor can detect the shape change, but the shape change along the traveling direction of the light path from the light source to the image sensor. Is generated, it does not affect the light shielding area, and as a result, the shape change cannot be detected.

Patent Literature 2 or Patent Literature 3 discloses a structure in which light is illuminated from the side of a screw thread and the reflected light is sensed. However, such a device may be able to recognize the presence or absence of a thread or a deformation, but it is not able to accurately recognize the deformation. Moreover, when unevenness | corrugation generate | occur | produces in a part of screw thread, the reflected light of the said unevenness | concentration is received.

That is, although the conventionally known inspection apparatus may be able to detect some kind of defective products, it may not be recognized as defective depending on the degree of shape change, and there existed a problem that it could not detect with high precision.

However, although the detection accuracy can be improved by irradiating light with time from a plurality of angles using a large number of light sources, the screw is small and it is not easy to detect unevenness generated by the deformation of the thread with high sensitivity. not.

Patent Document 1: Japanese Patent Laid-Open No. 62-49203 Patent Document 2: Japanese Patent Application Laid-Open No. 5-240738 Patent Document 3: Japanese Patent Laid-Open No. 55-70702

This invention provides the inspection apparatus which can recognize well any deformation | transformation of a screw thread well.

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, the thread inspection apparatus which concerns on this invention is the light source part which illuminates the outer surface of a rotating screw partly or continuously, the imaging sensor which receives the reflected light from a screw, rotation information and imaging of a screw. In the structure having an image processing unit for recognizing the shape of a thread based on information, the imaging sensor does not recognize the reflected light when the thread shape is normal, but is caused by the unevenness only when unwanted unevenness exists in the thread. At least the area | region which can receive the reflected light is characterized by observing.

Moreover, two said light source parts are formed, and it is characterized by illuminating the said screw thread from the front and rear of the rotation direction of a screw with respect to the said area | region.

In addition, the light source unit is characterized in that the emission wavelength is different.

In the thread inspection device according to the present invention, since the imaging sensor is disposed at a position to receive the reflected light from the screw surface only when the unevenness is formed on the thread, the unevenness formed on the screw can be reliably detected. Further, by providing two light sources for emitting light of different wavelengths, it becomes possible to more accurately grasp the shape of the unevenness from the lightness or color characteristics of the captured image.

1 shows a schematic configuration of a thread inspection device according to the present invention.
2 shows a schematic configuration of a thread inspection method according to the present invention.
3 shows a schematic configuration of a thread inspection method according to the present invention.
4 shows a schematic configuration of a thread inspection method according to the present invention.
5 is a conceptual diagram for explaining a thread inspection device according to the present invention.
Fig. 6 shows a diagram for explaining a conventional inspection device for screw threads.

1 shows a schematic configuration of a thread tester according to the present invention. The screw to be inspected is attached to the rotating portion 1a of the holder 1. The screw is rotated by the rotating section 1a in the direction of illustration, that is, the direction when screwing with the female screw. Radiated light from light sources 2 (2a, 2b) passes through diffuser plates 3 (3a, 3b) to illuminate the outer surface of the screw. By the presence of the diffusion plates 3 (3a, 3b), the entire lengthwise direction of the male screw can be illuminated. In addition, the length of a male screw is about 2-3 mm, for example. In addition, FIG. 1 abbreviate | omits the lens, imaging sensor, and image processing part mentioned later.

FIG. 2 shows a state of the inspection apparatus shown in FIG. 1 as viewed from above. The light source 2a, the light source 2b, and the diffuser plate 3a and the diffuser plate 3b are arranged in line symmetry with the virtual line A connecting the screws, the lens 4, and the imaging sensor 5 therebetween. The light L1a and the light L2a emitted from the diffusion plate 3a are reflected on the screw surface and enter the imaging sensor 5 through the lens 4. Similarly, the light L1b and the light L2b emitted from the diffuser plate 3b are also reflected at the screw outer surface and enter the imaging sensor 5 through the lens 4. The input information of the imaging sensor 5 is transmitted to the image processing unit 6, and the image processing unit 6 has the entire screw based on the light information from the imaging sensor 5 and the rotation information from the holder 1. The shape of the circumferential surface can be recognized. In addition, as the imaging sensor 5, an area sensor having an area corresponding to the size of the screw is used.

The lens 4 introduces the reflected light in the area a of the screw outer surface among the radiated light of the light source 2a and the reflected light in the area b of the outer surface of the screw among the emitted light of the light source 2b. Radiated light from the light sources 2 (2a, 2b) passes through the diffuser plates 3 (3a, 3b), and also in screw outer surface regions (e.g., areas c) other than the areas (area a, area b). Illuminate. However, these illumination lights are not introduced into the lens 4 from the relation of the incident angle. Therefore, when the shape of the screw thread is normal, only the screw shapes in the areas a and b are received by the imaging sensor 5.

FIG. 3 shows a view for explaining an optical path between a light source and a lens when the shape of the thread is normal. In addition, the thread and the valley of the screw are continuously formed in the vertical direction of the page, but the shape of the thread is not shown to show the state in which the screw is cut in the cross section.

In the figure, in the area (area a) formed between the position P1a at which the light L1a passing through the diffusion plate 3a as the radiated light of the light source 2a irradiates the screw outer surface, and the position P2a at which the light L2a irradiates the screw outer surface. Reflected light is introduced into the lens 4. Similarly, in the area | region (area b) formed between the position P1b which light Llb which passed the diffuser plate 3b as radiation light of the light source 2b irradiates a screw outer surface, and the position P2b which light L2b irradiates a screw outer surface. Reflected light is also introduced into the lens 4. On the other hand, when the area | region (area c) separated from the area a was irradiated like the light L3a, the reflected light is not introduce | transduced into the lens 4, for example. Therefore, the imaging sensor not shown recognizes the reflected light from the area a and the reflected light from the area b simultaneously with respect to the rotating screw, but does not recognize the reflected light in the area c. In addition, in the longitudinal direction of the screw (the direction in which the screw advances when the screw is rotated), the entire region of the screw thread portion can be illuminated simultaneously by the diffusion plates 3 (3a, 3b). For this reason, when the screw is rotated at least once, the image processing part 6 can grasp | shape the shape of the whole threaded part.

4 is a diagram illustrating an optical path between a light source and a lens in a case where the shape of the thread is not normal and unwanted irregularities exist in a part of the thread. As in FIG. 3, the reflected light in the area a and the reflected light in the area b are introduced into the lens 4 and received by the imaging sensor 5. On the other hand, the light L3a on the light source 2a side is reflected at the wall surface H1 of the unevenness in the area c, and the reflected light is also introduced into the lens 4. Further, the light L3b on the light source 2b side is also reflected on the wall surface H2 of the unevenness in the area c, and the reflected light is similarly introduced into the lens 4. That is, if the shape of the thread is normal, the reflected light in the area c is not introduced into the lens 4 in relation to the incident angle of the illumination light, but if unwanted unevenness exists in the thread, the reflected light on the wall surface of the unevenness It is introduced into the lens 4. This is a feature of the present invention.

Moreover, in this invention, the wall surface H1 of unevenness | corrugation can be illuminated by the radiation light of the light source 2a, and the wall H2 of unevenness | corrugation can be illuminated by the radiation light of the light source 2b. Thus, by arranging the two light sources in the opposite directions to the center, the reflected light of the wall surface H1 and the wall surface H2 can be detected simultaneously, and as a result, the uneven shape can be detected more accurately. More specifically, since the screw is rotating, it may be possible to recognize any abnormality by the reflected light when the unevenness is located in the area a or the area b. As can be seen, irregularities cannot be recognized accurately.

5 shows a light receiving state by the imaging sensor 5 (area sensor). The state in the instant when there is a rotating screw is shown. (a) corresponds to FIG. 3 and shows the case where the shape of a thread is normal, (b) corresponds to FIG. 4, and shows the case where unwanted unevenness | corrugation was formed in a part of thread.

In (a), the imaging sensor 5 receives the reflected light in the area a based on the light source 2a and the reflected light in the area b based on the light source 2b, but does not receive the reflected light from the area c. not. For this reason, the corresponding area | region of the area c does not recognize any image. On the other hand, in (b), the imaging sensor 5 receives the reflected light in the area a based on the light source 2a and the reflected light in the area b based on the light source 2b in the same manner as in (a). Also in c, the light reflected from the wall surface of the unevenness is received.

As described above, according to the present invention, the unevenness of the thread can be detected by detecting the reflected light from the area that the image pickup sensor 5 originally receives.

The light source 2 emits visible light, for example, LED is employed. In addition, in FIG. 1 and FIG. 2, it is preferable that the light source 2a and the light source 2b respectively radiate the light (light of a different color) of a different wavelength. For example, the light source 2a uses LEDs emitting red light, and the light source 2b uses LEDs emitting blue light. This advantage is that the appearance of the unevenness is detected by detecting images with different shades and color characteristics, respectively, on the wall surface reflected by the light of one light source and the wall surface reflected by the light of the other light source for one unevenness. This is because the shape can be specified more clearly. For example, in the case of Fig. 5B, when the red image G1 and the blue image G2 are recognized, the combined portion of red and blue is one unevenness, and the unevenness can be distinguished from the directions of red and blue. Moreover, it can be judged that the part connected with the envelope of these images is the magnitude | size of an unevenness | corrugation. In addition, it is possible to distinguish between irregularities generated in close proximity. However, if the light source 2a and the light source 2b are the same, the image G1 and the image G2 are recognized as the same pattern, the image G3 existing in the vicinity thereof is also recognized the same, and irregularities are formed by the combination of any images. It becomes difficult to specify whether there is. As described above, the present invention is also characterized by illuminating light of different wavelengths (lights of different colors) from opposite directions, respectively.

The imaging sensor is preferably a CCD camera capable of capturing color images. In addition, by adjusting the lens, the distance to the screw thread and the focus can be adjusted. In addition, in the said embodiment, although demonstrated using the area sensor as an imaging sensor, it may be a line sensor. In this case, the same effect can be achieved by using only the area c as a light receiving area as a line sensor.

The diffusion plate 3 is made of, for example, an acrylic resin plate or the like. By diffusing the illumination light to the screws, it enables illumination from all directions. Thereby, unevenness | corrugation can be detected more accurately.

In the above embodiment, the case where the light source 2 and the diffuser plate 3 are fixed and the entire length of the screw can be illuminated at the same time has been described. For example, in the case where the total length of the screw is long, for example, (2) and the diffusion (3) are integrally moved in the full length direction of the screw, and it is also possible to illuminate the outer surface of the screw with the movement.

1, 2, 3, 4, and 5 are very schematically illustrated for convenience of describing the invention. For this reason, the angle and direction, such as an incident angle and a reflection angle, are not necessarily described optically correctly. The screw also represents only a screw thread and a valley portion, but in reality, the screw head and the trunk portion exist.

1: holder
2: light source
3: diffuser plate
4: lens
5: imaging sensor
6: image processing unit

Claims (3)

Inspection of the screw thread having a light source part that partially and continuously illuminates the outer surface of the rotating screw, an imaging sensor that receives the reflected light from the screw, and an image processing part that recognizes the shape of the thread based on the screw rotation information and the imaging information. In the device,
The imaging sensor does not recognize the reflected light when the thread shape is normal, but inspects at least the region capable of receiving the reflected light due to the unevenness only when unwanted unevenness exists in the thread. Device. The method according to claim 1,
Two light source units are formed,
The said thread thread is illuminated with respect to the said area from the front and rear of the rotation direction of a screw, The thread inspection apparatus characterized by the above-mentioned. The method according to claim 2,
The light source unit is a thread inspection device, characterized in that different radiation wavelengths.

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