JPS5834775B2 - Defect inspection equipment - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a defect inspection apparatus, and more particularly to a defect inspection apparatus for detecting defects present on the surface of a rod-shaped object to be inspected having a substantially circular cross section.

An example of an object to be inspected having a circular cross section is a welding rod.

In this welding rod manufacturing process, in order to guarantee quality such as the performance and commercial value of the welding rod during use, a visual inspection is carried out to check for surface defects on the welding rod immediately before packaging, which is the final process.

By the way, welding rods often have defects such as chips and scratches where paint flux is partially missing, and cracks where cracks open in the flux, mainly during the painting or drying process of welding rod manufacturing, at the ends. These defects must be detected to ensure the quality of welding rods.

Therefore, in the final process, the surface shape of the end of each welding rod is visually inspected by an inspector, and the defects are sorted by type and size.

In this visual inspection, in which the inspector visually inspects the surface of the end of each welding rod, the work takes a long time, and as the inspection speed increases, the fatigue of the inspector increases rapidly. There is a risk that the inspector's decision-making ability will deteriorate, leading to inspection errors, etc.

In other words, there was a problem in that even if there was a defect in the surface shape of the end of the welding rod, it could be selected as a good product.

SUMMARY OF THE INVENTION An object of the present invention is to provide a defect inspection device that can detect defects occurring at the end of an object to be inspected, such as a welding rod, at high speed and accuracy.

The outline of this objective is to scan a thin beam of light multiple times in the diameter direction of the object to be inspected while the object to be inspected moves through the inspection area and makes one rotation, and to block the object for each scan. The width value corresponding to the thickness of the object to be inspected obtained by By inspecting the object to be inspected and scanning the object with a narrow diameter light, the amount of change in light due to shielding with the object to be inspected is increased, reducing the processing time per object and detecting defects. Improved accuracy.

DESCRIPTION OF THE PREFERRED EMBODIMENTS The structure and effects of an embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a conveying device that conveys a round bar 10, which is an object to be inspected, in the direction of the arrow mark.

This conveyance device conveys a round bar to be inspected in a direction perpendicular to the longitudinal direction of the round bar by means of two sets of belt conveyors 11 and 12. The round bars are made to perform rotational motion, that is, rotational motion, by varying the feeding speeds of the conveyors of the set.

Note that the belt conveyor is driven by a drive section (not shown).

FIG. 2 shows a detection unit that detects defects present at the end of a round bar that is transported while rotating.

This detection unit includes a light source 13 that emits a thin light, a scanning mirror 14 that reflects the light from the light source and scans the round bar at the end position and along the conveying direction of the round bar being conveyed by the conveying device, and a scanning mirror 14 that reflects the light from the light source and scans the round bar along the conveying direction. A first optical system 15 is placed between the mirror 14 and converts the scanning light into parallel light; and a first optical system 15 is placed between the round bar and the first optical system to convert the scanning light that has passed through the first optical system into a single point. It consists of a second optical system 16 for condensing light, a photoelectric converter 17, and a preamplifier 18 for amplifying the converted electrical signal, and the round rod rotates at least once while it crosses the inspection area determined by the optical system. However, the scanning light is made to scan the end of the round bar multiple times.

FIG. 3 shows a processing device that determines whether or not there is a defect at the end of a round bar based on the electrical signal from the detection section.

This processing device has a built-in waveform shaping circuit 19 that shapes the waveform of the output signal of the amplifier 18, and a pulse generator 20, and the pulse width corresponding to the round bar of the output signal of the waveform shaping circuit 19 is determined by the number of pulses of the pulse generator. a first setting device 22 that sets the diameter of the round bar as the number of pulses;
A subtraction circuit 23 that outputs a signal obtained by subtracting the number of output pulses of the gate circuit from the number of pulses of the first setter, a second setter 24 that sets the number of pulses corresponding to the defect, and a second setter 2
It is composed of a comparison circuit 25 that outputs a signal obtained by comparing and determining the output value of the subtraction circuit 23 from the set pulse number of 4, and the entire circumference of the end of the round bar passing through the inspection area is detected from the output of the comparison circuit 25. Make it.

Next, the operation of the device configured as described above will be explained.

The round bar is rotated at least once while being conveyed in the inspection area scanned by the light beam, and the conveying device is configured to convey the round bar so that there is no more than one round bar within the inspection area.

Further, since the light is scanning in the inspection area, the round bar passing through the inspection area is scanned multiple times (three times in the figure) by the light beam scanning in the diametrical direction during one rotation.

A signal (
Figure 4A) is output.

In Figure 2, during the first scan, the round bar is at position A,
During the second scan, the round bar is located at position B, and during the third scan, the round bar is located at position C.

By the way, if we assume that the transport speed, rotation speed, and scanning speed of light of the round bar are constant, the time that the round bar interrupts is almost constant.

However, if there is a chip or scratch on the round bar at the location where the light is scanned, the time blocked by the round bar will vary.

In other words, in Figure 2 B-C, the influence of the chip appears, and the pulse width is shorter than that blocked by a round bar with a normal diameter, and in Figure 2 A, there is a chip directly below, but the scanning due to the chip is There is no part where light is applied, and a signal with a pulse width almost equal to that of a round bar with a normal diameter is obtained.

Under such circumstances, a signal containing a pulse width proportional to the diameter of the round bar is output from the photoelectric conversion element.

The pulse width signal proportional to the diameter of this round bar is sent to the gate circuit 2.
1 generates a pulse from the pulse oscillator 20 (Fig. 4B)
) (FIG. 4C), and the subtraction circuit 23 calculates the difference from the first set value corresponding to the diameter of a normal round bar.

That is, if there is no defect, the contents of the subtraction circuit will be zero; if there is a defect, a number of more than a few pulses will remain.

The content of this subtraction circuit is compared and determined with the defect setting signal in the comparison circuit 25, and when the content is higher than the defect setting signal, the comparison circuit 25
5 outputs a determination signal indicating the content in which the defect exists.

Note that while the round bar crosses the inspection area once, the light beam scans three times to inspect the entire circumference of the end of the round bar, so the comparison circuit 25 scans the round bar three times. The respective outputs are accumulated, and when the round bar leaves the inspection position, if there is a defect in the information for three times using a fourth operation signal, a signal indicating that the round bar is defective is outputted and the inspection is performed.

Next, another embodiment will be described with reference to FIG.

Devices having the same functions as those shown in FIG. 3 are labeled with the same tolerance, and the explanation thereof will be omitted.

In order to irradiate the end of the round bar at the location where the bar 10, which is the inspection area, moves once in the direction of the arrow sign while moving in the arrow resistance direction, the end of the round bar is irradiated.
A rod-shaped light source 26 is arranged to illuminate a surface perpendicular to the direction of movement of this end.

Light from this rod-shaped light source is guided to a detector 27 whose field of view is the inspection area.

This detector has a photoelectric converter 27B in which a plurality of photoelectric conversion elements are arranged in a straight line at a predetermined time interval at a light collection position of a light collection optical system 27A, and the plurality of photoelectric conversion elements of this converter The output terminals of 1 are scanned one after another, a digital amount proportional to the diameter of the round bar is extracted from the number of elements that are not producing an output, and this digital amount is applied to the subtraction circuit shown in Fig. 3.
It is also possible to take the difference from the set value.

It goes without saying that the same effect as the present invention can be achieved by replacing the detector with a television camera and manually inputting the pulse signal of the round bar component contained in the video signal to the waveform shaping circuit shown in FIG.

Moreover, it goes without saying that the present invention can be implemented without using a photoelectric converter consisting of a plurality of photoelectric conversion elements.

That is, the pulse width of the component in the diameter direction of the round bar obtained by scanning the field of view of the detector is compared with a set width value, and the presence or absence of a defect is determined from this comparison signal.

As described above, the present invention is configured so that the entire circumference of the round bar is inspected by scanning the light beam multiple times in the diametrical direction while the round bar moves once in the inspection area. This defect inspection device eliminates the need to stop for inspection, and improves detection sensitivity by scanning the rotating round bar with a thin beam of light, allowing for accurate defect inspection at high speeds. can be provided.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of a conveying device for conveying round bars, FIG. 2 is a schematic configuration diagram of an optical detection section of the present invention, FIG. 3 is a diagram showing a processing device in block configuration, and FIG. The figure shows the output waveform at each point, and FIG. 5 is a diagram showing another embodiment of the present invention. 10... Circle L11, 12... Belt conveyor, 13... Light source, 14... Scanning mirror, 15, 16... First , second optical system, 17.
...Photoelectric conversion element, 20...Pulse oscillator, 21...Gate circuit, 22゜24...
...First and second setter, 23...Subtraction circuit, 2
5... Comparison circuit, 26... Light source, 27
······Detector.

Claims (1)

[Scope of Claims] 1. A light source that emits beam-shaped light, a conveyance device that rotates a round bar without overlapping and conveys it in a direction perpendicular to the rotation axis, and A scanning mechanism that scans the round bar multiple times in the right angle direction during one rotation of the round bar, and a photoelectric conversion unit that inputs the scanning beam light and generates a pulse with a width proportional to the thickness of the round bar by shielding the round bar. , and a circuit that compares this pulse width value with a width setting value corresponding to the thickness of the round bar and outputs a signal for determining whether or not there is a defect in the round bar. 2. A light source that emits light in the form of a band, a conveying device that rotates a round bar without overlapping within the band-shaped light area and conveys it in a direction perpendicular to the axis of rotation, and a light source that emits the band-shaped light within the field of view. A photoelectric conversion unit that scans multiple pieces along this strip direction during one rotation of the round bar and outputs a signal with a digital amount or pulse width proportional to the thickness of the round bar by shielding the round bar, and the converted output amount. A defect inspection device comprising: a circuit that compares the data with a set value corresponding to the thickness of the round bar and outputs a signal for determining the presence or absence of a defect in the round bar.