JPH0449063B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an apparatus for optically inspecting defects on the surface of a threaded portion during a thread processing process.

Conventionally, devices have been developed to inspect screw elements such as "thread height" and "thread pitch." A particular problem is that the profile of a normal surface is extremely complex, and the curved surface changes with a small radius of curvature, making it difficult to use optical methods, which are the typical method for surface inspection.

This invention was made to deal with the current situation, and the present invention scans the incident light on a plane that intersects the outer circumferential circle of the trough of the screw, is parallel to the central axis of the screw, and does not include the central axis of the screw. By irradiating the light in a spot-like manner on the surface of the screw, the reflected light from the surface of the screw is reflected on the so-called screw surface (hereinafter referred to as the screw surface) of the crests, troughs, and slopes connecting the crests and troughs. By spatially separating and reflecting light from the ridges (referred to as ridges), and detecting changes in the signal waveforms obtained by receiving the reflected light with independent photoelectric conversion elements, The object of the present invention is to provide a screw surface defect inspection device that can independently detect defects in each of the troughs and ridges.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

Fig. 1 is a conceptual diagram showing the optical system of the inspection device according to the present invention, Fig. 2 is a plan view showing the path of reflected light at the threaded portion of the optical system shown in Fig. 1 viewed from above, and Fig. 3 A. B, C are waveform diagrams showing output signal waveforms of each photoelectric conversion element, respectively.

In the figure, 1 is the screw, 2 is the incident light scanning the surface of the screw 1, 3 is the reflected light reflected from the crest of the screw 1, 4 is the reflected light reflected from the ridgeline of the screw 1, and 5 is the screw The reflected light reflected from the valley of 1,
6, 7, and 8 are photoelectric conversion elements that receive each reflected light beam 3, 4, and 5 and output a signal obtained by photoelectric conversion; 9 is the outer circumference of the peak of the screw 1; and 10 is the valley of the screw 1. 20 is the output signal waveform of the photoelectric conversion element 6, 2
1 is the output signal waveform of the photoelectric conversion element 8, and 22 is the output signal waveform of the photoelectric conversion element 7. Note that the symbols a, b, and c in Fig. 3 indicate the same points in time, and a and c are the troughs of the screw, and b is the crest of the screw, respectively, with the incident light 2. It shows the point in time.

In Fig. 1, the incident light 2 intersects the outer circumferential circle 10 of the valley of the screw 1, scans a plane parallel to the central axis of the screw, and does not include the central axis of the screw, and forms a spot on the surface of the screw. It is irradiated in a condensing manner.

At this time, as shown in FIG. 2, reflected light 3 is generated from the irradiation point of the ridge of the screw 1 of the incident light 2 in a direction different from that of the incident light 2. Similarly, reflected light 5 is generated from the irradiation point of the trough of the screw 1 of the incident light 2 on the screw 1 in a direction different from that of the incident light 2.

Here, since the angle between the surface of the screw and the incident light 2 is different between the irradiation point at the peak of the screw 1 and the irradiation point at the trough of the screw 1, as shown in the figure, the reflected light 3 and the reflected light 5 and their routes are largely separated spatially. Then, reflected light 4 from the ridgeline portion of the screw 1 is generated between the paths of these two reflected lights.

On the other hand, since the incident light 2 is scanned parallel to the central axis of the screw 1, each thread, thread valley, etc. on the screw 1,
Each of the reflected lights from the thread ridgeline occurs on a straight line, that is, in the directions of the reflected lights 3, 5, and 4 in FIG. 2, respectively. Therefore, each of the reflected lights 3, 5, 4 is received and photoelectrically converted by each of the photoelectric conversion elements 6, 8, 7, which have a shape elongated in a direction parallel to the central axis of the screw 1, thereby converting the reflected light of the screw 1. Electrical signals corresponding to each region can be obtained.

FIG. 3 shows an example of the electric signal obtained in this way, where 20 is the output signal waveform corresponding to the thread, 21 is the output signal waveform corresponding to the screw root, and 22 is the output signal waveform corresponding to the ridge of the screw. The corresponding output signal waveform.

As shown in the figure, as the light scans, that is, with the passage of time, first a pulse-like output signal of an output signal waveform 20 is generated, and then an output signal waveform 22 and an output signal waveform 21 are generated in this order. At this time, each signal waveform is not affected by the reflected light from other parts because the reflected lights 3, 4, and 5 received by the photoelectric change elements 6, 7, and 8 are largely separated spatially. A stable output signal waveform can be obtained. Also,
If a defect occurs in each part of the screw 1, the reflected light of the corresponding part will be disturbed as shown in FIG. 3, and the corresponding output signal waveforms 20, 21, and 22 will also be disturbed, so it is necessary to detect this. Defects in each part of the screw 1 can be extracted independently.

Therefore, according to the present invention, it is not only possible to stably perform a defect inspection on the entire surface of the screw 1, but also to obtain information on which part of the surface of the screw 1 has a defect. . Although not specifically illustrated, circuit means for detecting abnormalities and extracting defects from pulse waveforms as shown in Fig. 3 are already well-known for defect inspection, and the specifics of the signal processing circuit are known. Examples may not go beyond the scope of the claims.

In the above embodiment, the case where the incident light is scanned in the direction along the central axis of the screw 1 has been described, but when the external profile of the screw 1 has a shape other than a cylinder, for example, a conical shape, The same effect as described above can be obtained by scanning the light in the direction along this profile.

Further, the scanning angle, that is, the angle at which the incident light is scanned, must be set so that the valley of the screw 1 does not fall into the shadow of the crest of the screw 1. That is, the scanning angle must be set so that the entire screw surface in the plane scanned by the incident light is irradiated with the incident light. The range in which this scanning angle can be set varies depending on the diameter of the screw, the angle of the screw thread, and the distance between the plane scanned by the incident light and the center of the screw. Conditions must be met.

As described above, according to the present invention, incident light is scanned on a plane that intersects the outer circumference of the trough of the screw, is parallel to the central axis of the screw, and does not include the central axis of the screw, and is scanned in the form of a spot on the surface of the screw. By irradiating the light so as to focus it on the screw, and detecting the change in the photoelectrically converted signal waveform by receiving the reflected light separated from each part of the screw, the screw This method not only makes it possible to inspect surface defects on surfaces, but also makes it possible to identify the defect occurrence site, which has great practical effects.

[Brief explanation of the drawing]

Fig. 1 is a conceptual diagram showing the optical system of the inspection device according to the present invention, Fig. 2 is a plan view showing the path of reflected light at the screw portion, and Fig. 3 A, B, and C are output signals of each photoelectric conversion element. FIG. 3 is a waveform diagram showing waveforms. In the figure, 1 is a screw, 2 is incident light, 3, 4, 5 is reflected light, 6, 7, 8 are photoelectric conversion elements, 20, 21,
22 is an output signal waveform. Note that the same reference numerals in each figure indicate the same or equivalent parts.

Claims (1)

[Scope of Claims] 1. A screw surface defect inspection device for inspecting defects on the surface of the screw using reflected light by irradiating incident light condensed into a spot on the surface of the screw. Scan a plane that intersects the outer circumferential circle of the screw root, is parallel to the central axis of the screw, and does not include the central axis of the screw, and irradiates the entire surface of the screw within the irradiation area of the incident light. , the crest of the above screw,
A surface defect inspection device for a screw, characterized in that the reflected light generated spatially separately from each of the troughs and the ridges is received by independent photoelectric conversion elements. 2. The screw surface defect inspection device according to claim 1, wherein the scanning direction of the incident light is set along the profile of the screw.