JPH0510742A - X-ray inspection apparatus and method of insulated cable - Google Patents

Abstract

PURPOSE:To distinguish the boundary of a conductor and an insulating layer and foreign substances clearly and detect inclination of a cable and foreign substance mixing precisely by binary-processing the X-ray images. CONSTITUTION:An inspection apparatus 1 is composed of mainly two X-ray sources 5a, 5b to radiate X-ray to an insulated cable 4 moving in the inside of a cross-linking tube 3, cameras 6a, 6b to focus the X-ray transmitted through the insulated cable into an image, an X-ray image processor 7 connected with each of the cameras 6a, 6b, and a microcomputer 8 to calculate and determine whether inclination or foreign substance exists or not based on the signals from the X-ray image processor 7. The X-ray transmitted through the insulated cable 4 is focused into an image by the camera 6a, 6b and the X-ray image is binary-processed to detect the boundary of the conductor and the insulating layer and the foreign substance as binary signals. The binary signals are processed to correct the strain of the image in both X, Y directions. Based on the signals after correction which correspond to the image, the thickness of the insulating layer is computed and at the same time the existence of foreign substance in the insulating layer is determined.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an apparatus and method for inspecting an insulated cable such as a CV cable, and more particularly to an apparatus and method for inspecting an insulated cable equipped with an X-ray image processing apparatus for seeing through the cable online.

[0002]

CV cables having a cross-linked polyethylene insulation layer in the coating layer are generally produced by extrusion coating the insulation layer on a conductor by means of an extruder and then continuously crosslinking the cable with a cross-linking tube. Such a CV cable is required to have no uneven thickness and no foreign matter is mixed into the insulating layer, and it is desired to detect such uneven thickness and foreign matter online during CV cable manufacturing.

As a method for monitoring uneven thickness when manufacturing a CV cable,
An X-ray inspection device is installed on the vulcanization cylinder to check the X
A method in which a line image is projected on a fluorescent screen and the uneven thickness of the insulating layer is monitored from this X-ray image (Japanese Patent Publication No. 27132/1985).
No.), and further, an output corresponding to the length in the width direction is generated from the X-ray image of the electric wire to calculate and display the coating thickness, uneven thickness, and the like, and a coating thickness measuring device has been proposed.

The present inventors have further developed an improved coating thickness measuring device which corrects the distortion of the X-ray image in such X-ray coating thickness measurement and enables accurate coating thickness measurement, and has filed a patent application. (Japanese Patent Laid-Open No. 2-138806). As shown in FIG. 8, this measuring device projects an X-ray image obtained by transmitting soft X-rays from an X-ray source 101 to a coated electric wire on a fluorescent screen 102, picks up this projected image and picks up the width of the electric wire image. Generate an output signal R ₁ of half the length r ₁ in the direction. Then, the output signal R ₁ is compared with the relative distances a and b between the respective positions of the X-ray source 101, the imaging device (fluorescent plate) and the covered electric wire W to calculate the covering thickness T of the covered electric wire. The error of the X-ray image due to the radial irradiation of the lines is corrected, and the accurate coating thickness measurement is enabled.

[0005]

However, in such conventional X-ray coating thickness measurement, since the X-ray image is visualized by the fluorescent plate and the signal is directly taken out from this image, the conductor and the coated portion are taken. There is a case that an error occurs because the boundary of is not clear, and it takes time from the analysis of the image to the correction and adjustment of the cable core, which makes it difficult to respond quickly online. Further, when the X-ray image is radially irradiated, the X-ray image is distorted not only in the width direction of the electric wire but also in the axial direction.
In the error correction of the line image, only the data of the portion where the X-rays intersect at right angles can be used as accurate data. Therefore, when slicing the image in the scanning direction, the error becomes large, so the calculation must be performed by one-cut processing of the image.

Further, in the conventional X-ray coating thickness measurement,
Since X-rays are radiated from only one direction of the cable, uneven thicknesses other than in one direction cannot be detected, and foreign matter cannot be detected.

[0007]

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned conventional problems, and it is possible to quickly and accurately detect the uneven thickness of the insulating cable and the mixing of the foreign matter online in the CV line and in the bridge pipe. It is an object of the present invention to provide an insulated cable inspection device and method capable of achieving the above. This invention
Further, it is an object of the present invention to provide an insulated cable inspection device and method that can quickly perform centering correction adjustment after detection of uneven thickness to manufacture a high-quality insulated cable without uneven thickness.

[0008]

The insulated cable inspection apparatus of the present invention which achieves the above object has an X-ray source provided outside the moving path in the bridge tube of the insulated cable being manufactured, and Based on an image forming means for forming an image of X-rays transmitted through the insulating cable, an image processing means for binarizing the X-ray image obtained by the image forming means, and a binarized signal from the image processing means. Calculation of wall thickness of insulation layer of insulated cable,
And an image intensifier camera (hereinafter referred to as II camera) as an image forming means, and more preferably as an X-ray source. 2 Xs orthogonal to each other
The X-ray source is provided with two image forming means and two image processing means respectively corresponding to these X-ray sources, and the computing means is provided for insulating the insulated cable based on the binary signal from the two image processing means. The calculation of the wall thickness of the layer and the determination of foreign matter are performed.

The insulated cable inspection method of the present invention is
The moving path of the insulated cable being manufactured is irradiated with X-rays, the X-ray image of the insulated cable obtained by X-rays is binarized by image processing means, and insulation of the insulated cable is performed based on the binarized signal. The thickness of the layer is calculated and the foreign matter is determined, and preferably, the process of correcting the distortion in the moving direction of the insulated cable of the X-ray image is performed.

[0010]

The image processing means enhances and binarizes the output corresponding to the insulating layer and the conductor of the X-ray image photoelectrically converted by the image forming means. As a result, the boundary between the insulating layer and the conductor and the boundary between the foreign matter and the insulating layer are output as a binarized signal. The binarized signal is converted into a signal corresponding to the length of the image in the widthwise direction, and is preferably corrected in the scanning direction by the computing means, and then input in advance to the outer diameter of the insulating layer and the outer diameter of the conductor. A predetermined calculation is performed based on data such as the size of the foreign matter to be detected. The calculating means calculates and outputs the outer diameter of the cable and the uneven thickness ratio, determines the presence or absence of a foreign matter, and displays it by a predetermined output means. Based on these indications, the centering bolt of the crosshead for positioning the conductor can be adjusted to promptly improve the roundness of the cable.

Here, when two X-ray images obtained by irradiating X-rays from two directions are used, more accurate calculation and determination can be performed. Further, when the II camera is used as the image forming means, the reaction is fast, so that the image processing can be performed promptly, and in particular, the mixing of foreign matter during movement can be found promptly.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The insulated cable inspection apparatus of the present invention will be described in detail below with reference to the embodiments shown in the drawings. As shown in FIG. 1, an insulated cable inspection device (hereinafter, simply referred to as an inspection device) 1 of the present invention is located near a part of a CV cable manufacturing device, preferably a crosshead 2 for adjusting the position of a conductor during extrusion molding. Is provided above the bridge pipe 3. This inspection apparatus 1 mainly includes two X-ray sources 5a and 5b for irradiating the insulated cable 4 which is moving in the bridge tube 3 with X-rays, and image formation for forming X-rays transmitted through the insulated cable as images. II as a means
Micro as a calculation means for calculating the uneven thickness ratio and the presence / absence of foreign matter by the signals from the cameras 6a and 6b, the X-ray image processor 7 connected to the II cameras 6a and 6b, and the X-ray image processor 8. And a computer 8.

As shown in FIG. 2, the bridge tube 3 has two sets of X-ray incident windows 51a and 51 corresponding to the two X-ray sources 5a and 5b.
b and X-ray transmission windows 52a and 52b are provided, and X-ray sources 5a and 5b are provided outside the X-ray incidence windows 51a and 51b.
Outside the X-ray transmission windows 52a and 52b, the II camera 6a,
6b are installed respectively. These X-ray sources 5a, 5
b irradiates weak soft X-rays of about 0.1 mR / Hr in the directions (X and Y directions) orthogonal to the axial direction of the cable 4 and intersecting with each other. The II cameras 6a and 6b use the X-ray source 5
X-ray transmission window 52a through the cable 4 through a and 5b,
The X-ray image transmitted to the 52b side is projected on the fluorescent plate 61, and the obtained X-ray image is picked up and output as an electric signal corresponding to the intensity of the X-ray.

As the image forming means, in addition to the II camera, known ones such as a fluorescent plate and a CCD camera can be used.
Since the camera is not subject to the reaction speed limitation due to the battery storage time unlike a line sensor type camera using a CCD, it is suitable for metal foreign matter detection and the like. Further, the reaction speed is faster than that of the fluorescent screen method, and it is particularly advantageous when online image processing is performed to control the conductor position.

The II cameras 6a and 6b are each driven and controlled by the controller 60, and if necessary, the raw image projected by the fluorescent screens of the II cameras 6a and 6b is visualized by the display means 71 such as a CRT. As shown in FIG. 3, the image processor 7 as the image processing means includes a memory / integrator 72.
4 and enhances an electric signal corresponding to the intensity of the X-ray of the image by a predetermined threshold value preset in the memory to binarize the electric signal, and photoelectrically converts the binarized electric signal again. It is visualized as an image as shown in.

In FIG. 4, a screen A is an image by X-rays in the x direction, and areas I and II correspond to areas I and II of the fluorescent screen 61A of the II camera 6a shown in FIG. Similarly, screen B is y
In the image by X-ray in the direction, regions III and IV are I shown in FIG.
It corresponds to regions III and IV of the fluorescent screen 6B of the I camera 6b.
As is clear from these figures, of the two metal pieces in the insulating layer P of the cable 4, one appears on both screens A and B, but the other appears only on the screen A. That is, all the metal pieces and the like can be detected only by X-ray fluoroscopy from both XY directions. Further, such a binarization process clarifies the outer peripheries of the conductor portion and the insulating layer portion.

The microcomputer 8 has a cable conductor diameter, a cable wall thickness, an uneven thickness ratio to be warned, a detected metal size,
Predetermined data such as the cable product name, tube voltage applied to the bridge tube, tube current, cable length, etc. are input in advance, and will be described later based on these input data and the electric signal from the image processor 7. A predetermined calculation. These calculation results are displayed on the display unit 9 such as a CRT together with the above-mentioned processed image and output to the printer 10. .

A specific example of the calculation method by the computer 8 will be described below. 1) Measurement of outer diameter (D) and wall thickness (t) First, assuming that the cable 4 does not move, FIG.
Since the position of the center 0 of the conductor C is determined by the crosshead centering bolt 4 in the X and Y directions, the distance a from the X-ray source 5a (x) to the cable center O
And the distance b from the cable center O to the camera screen 61 is determined. Further, the outer diameter d of the conductor C is measured by a caliper or the like in advance and the data is input.

On the other hand, the center S of the cable in the X-ray image
From the distance R ₂ from the distance R ₁ and the center S to the periphery to Q ₁ conductor C to the outer circumference Q ₂ of the insulating layer P is given by the following Equations 1 and 2. In other words, similar to the △ xOP ₁ and △ xQ ₁ S,
Since OP ₁ / xP ₁ = Q ₁ S / XS, when the radius of the conductor is r,

[0020]

[Equation 1]

Further, Δx0P ₂ and ΔxQ ₂ S are similar to each other, and O
Since P ₂ / xP ₂ = Q ₂ S / xS, when the cable radius is y,

[0022]

[Equation 2]

On the other hand, the thickness t of the insulating layer 2 is t = y−r, and from equations 1 and 2, y and r are respectively

[0024]

[Equation 3]

[0025]

[Equation 4]

Therefore,

[0027]

[Equation 5]

[0028] Here, if k = R ₂ / R ₁ ,
The thickness t of the insulating layer 2 is

[0029]

[Equation 6]

It becomes By introducing r = d / 2 in the formula 1, R ₁ is determined, also the R ₁ by the image processing R
_Since the ratio k to ₂ is obtained, the thickness t of the insulating layer 2 is obtained from Equation 6. On the other hand, the outer diameter D of the cable is D = d +
It is easily calculated by 2t. The above is a calculation only considering the case where the X-ray is irradiated in the plane orthogonal to the traveling direction of the cable (axial direction of the bridge tube 5), but in reality, as shown in FIG. Since the lines spread radially, the image is curved as it goes up and down from the plane (XS plane) orthogonal to the cable traveling direction.

Therefore, when the screen is sliced from the top to the bottom, an error will occur in the calculation result.
In order to prevent such an error, it is preferable to perform one-cut processing only on the XS plane or perform scanning correction as described below. 2) Scan correction In FIG. 7, assuming that the cable scanning interval is δ ₀ , Δ
xNN ₁ and ΔxSS ₁ , ΔxNN ₂ and ΔSS ₂ , ... Δx
Since NNn and ΔxSSn are similar to each other, the following equation holds.

[0032]

[Equation 7]

[0033]

[Equation 8]

[0034]

[Equation 9]

Therefore, the bending rate f (n) is

[0036]

[Equation 10]

Since R ₃ = D / 2 and a and b are constants as described above, the curvature rate f (n) can be obtained for each scanning interval (every n). Therefore, by correcting the curvature rate f (n) based on the scanning position for each scanning interval, it is possible to eliminate the error due to the expansion of the outer diameter. That is, by setting t _n = f (n) t and D = d + 2t _n , the scanning area can be corrected in the slimming process.

3) Detection of Foreign Substances Regarding contamination of foreign substances such as metals in the insulating layer P, first, of the remaining binarized substances, those having a size larger than a preset detection metal size were determined to be foreign substances and further detected. Only the foreign matter that has moved within the scanning section is determined as the foreign matter in the insulating layer P. Foreign matter that does not move is ignored as dust attached to the inside of the bridge tube 3 and the X-ray entrance window.

The above calculation and determination results are displayed on the display unit 9 such as a CRT together with the binarized image. That is,
The maximum, minimum, and average cable outer diameter (D), cable thickness (t), uneven thickness ratio (e), etc. are displayed, and when a foreign substance in the insulating layer P is detected, an alarm lamp and an alarm sound are displayed. Causes a warning. The operator adjusts each crosshead centering bolt 4 based on the display result of these display portions, the image, and the warning. Since the inspection device 1 is provided close to the crosshead, uneven thickness and foreign matter are detected before the crosslinking proceeds, so that it is possible to promptly deal with it and minimize the generation of defective products.

[0040]

As is clear from the above embodiments, according to the X-ray inspection apparatus and method for an insulated cable of the present invention, the X-ray image is binarized to accurately measure the coating thickness, It is possible to judge foreign matter. In particular, when image processing and correction are performed in consideration of the fact that X-rays are radially applied to the cable to be measured and that the cable is curved in the scanning direction, slicing processing of the image becomes possible, and the outer diameter of the cable and the insulating layer The thickness of can be measured very accurately. Further, according to the X-ray inspection apparatus and method for an insulated cable of the present invention, since the CV cable is seen through from at least two directions, it is possible to detect all the foreign substances mixed in the cable.

Further, since the centering bolt is adjusted based on the result of the X-ray image processing, it is possible to quickly remove the uneven thickness of the CV cable and increase its roundness.

[Brief description of drawings]

FIG. 1 is a diagram showing an entire embodiment of an X-ray inspection apparatus for an insulated cable of the present invention.

FIG. 2 is a sectional view of a main part of the X-ray inspection apparatus.

FIG. 3 is a block diagram showing the configuration of the X-ray inspection apparatus.

FIG. 4 is a diagram showing a binarized image.

FIG. 5 is a diagram showing an X-ray fluoroscopic image.

FIG. 6 is a diagram for explaining a calculation method by a microcomputer.

FIG. 7 is a diagram illustrating a calculation method by a microcomputer.

FIG. 8 is a diagram showing a conventional coating thickness measuring device.

[Explanation of symbols]

1 ... Insulated cable inspection device 2 ... Crosshead 3 ... Bridge pipe 4 ... CV cable 5a, 5b ... X-ray source 6a, 6b ... II camera (image forming means) 7 ... Image processor (image processing means) 8 ... Microcomputer (calculation means)

Continued front page    (72) Inventor Mitsuyuki Tokuda             2-1-1 Oda Sakae, Kawasaki-ku, Kawasaki-shi, Kanagawa             No. Showa Densen Denki Co., Ltd. (72) Inventor Hideaki Honma             5-19-18 Higashi-Kashigaya, Ebina City, Kanagawa Prefecture               Softechs Co., Ltd. Ebina Factory

Claims (2)

[Claims] 1. An X-ray source provided in a moving path of an insulating cable being manufactured, an image forming means for forming an image of X-rays transmitted through the insulating cable from the X-ray source, and the image forming means. Image processing means for binarizing the X-ray image obtained by the above, and computing means for computing the thickness of the insulating layer of the insulated cable and determining foreign matter based on the binarized signal from the image processing means. An insulated cable inspection device characterized by being equipped with. 2. A moving path of an insulated cable being manufactured is irradiated with X-rays, an X-ray image of the insulated cable obtained by the X-rays is binarized by an image processing means, and this binarized signal is obtained. Based on the above, an insulated cable inspection method is characterized in that the thickness of the insulating layer of the insulated cable is calculated and foreign matter is determined.