JPH09304412A - Detecting equipment for foreign matter in transparent fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the presence of foreign matters and the size, by emitting a laser beam in the direction intersecting the flow of transparent fluid, detecting the change of received light amount which is caused by the presence of mixed foreign matters in the fluid, and correcting it on the basis of velocity data of the foreign matters. SOLUTION: Laser beams La, Lb which are emitted from a laser beam irradiation equipment 10 and split by a half mirror 20 are rectangularly refracted in parallel planes by mirrors 21a and 21b. Further the beams La and Lb are refracted in the axial line direction of a transparent ring 2 and in the direction rectrangular to the axial direction, by mirrors 22a and 23b or the like, respectively, and pass the transparent ring 2. The laser beams La and Lb which have passed the transparent ring 2 are received by light receiving equipments 30a, 30b. Digital signals outputted from the light receiving equipments 30a, 30b are processed by a signal processing equipment 40. The number of foreign matters, the size in the width direction, the position in the width directions, the flow velocity of the detected foreign matures, and correction coefficients based on the flow velocity are calculated, and outputted to an output equipment 50 and a monitor 60.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter detecting device for detecting the presence or absence and the size of foreign matter mixed in a transparent fluid by using a laser beam.

[0002]

2. Description of the Related Art In recent years, as a high-voltage power cable,
CV cables using cross-linked polyethylene for the cable insulating layer are frequently used. In this CV cable, polyethylene with a cross-linking agent is usually extruded from the extruder to cover the outer circumference of the inner semi-conductive layer on the cable conductor, and then the outer circumference of the outer semi-conductive layer is extruded and covered, and then pressurized in the cross-linking pipe. It is manufactured through a process of heating in the state and reacting a crosslinking agent to crosslink polyethylene. Generally, when constructing a long-distance power cable line using a CV cable,
After the CV cable is laid along the cable route for each short span, the front and rear ends thereof are sequentially connected, and the terminal connection portion is installed at the end of the line. Various methods have been developed for connecting the CV cable, but among them, EMJ
The (extrusion mold joint) method and the BMJ (block mold joint) method tend to be widely adopted in terms of insulation performance and reliability. The EMJ method involves assembling a mold around the conductor connecting part of a power cable in which the cable insulating layer and the semi-conductive layers inside and outside are penciled, and the exposed cable conductors are connected by a conductor sleeve, and polyethylene with a cross-linking agent is added. Introduced into the mold from the extruder,
It heats and pressurizes polyethylene to cross-link it. Further, in the BMJ method, a polyethylene block containing a cross-linking agent formed in advance into a semi-cylindrical shape is assembled into a cylindrical shape around a conductor connection portion of the power cable, or the polyethylene block containing a cross-linking agent formed in advance into a cylindrical shape is used as the above-mentioned. It is inserted into a conductor connection portion of a power cable, a mold is arranged on the outer periphery thereof, and the polyethylene is molded and integrated by heating and pressurizing and crosslinked.

Since the above-mentioned cable insulating layer of the power cable and its molded joint portion are used under a high electric field, metal powder, dust, or burns (heat-deteriorated material of resin material) are contained therein. If such foreign matter is mixed in, there is a possibility that they may become starting points and cause dielectric breakdown. Further, while the power cable is used for a long period of time, a water tree or the like may be generated around the foreign matter, and the insulation performance may be gradually deteriorated. Therefore, the insulating material used for the cable insulation layer of the power cable and the mold joint part is thoroughly inspected for foreign substances before being supplied to the extruder, and also in the extrusion process and the molding process. Careful attention is paid so that the resin does not become foreign matter due to excessive heating or retention and the insulation performance is not degraded.

[0004]

Various methods have been developed and put into practical use as methods for inspecting foreign substances in a resin material used as an insulating material for power cables, but each method has advantages and disadvantages. For example, the resin pellets before being supplied to the extruder are extracted and visually inspected for the presence and degree (size and number) of foreign matter, or the resin material extruded from the extruder is formed into a film, and There is known a method of irradiating a laser beam to determine the presence or absence and degree of a foreign substance from a transmitted image, but there is a concern about the reliability of each of these methods because they are not all inspections. Further, a method is also known in which a transparent window is provided in the resin passage at the tip of the extruder, a laser beam is emitted from the transparent window and scanning is performed, and the presence or absence and the degree of foreign matter are determined from the change in the intensity of the transmitted light. However, in this method, since the foreign matter in the resin flows together with the resin, the size of the foreign matter, particularly the size in the flow direction, cannot be accurately measured.

An object of the present invention is to provide a foreign matter detecting device in a fluid, which can accurately measure the presence or absence of a foreign matter and its size when detecting a foreign matter with a laser beam.

[0006]

A foreign matter detecting device in a fluid according to the present invention irradiates a transparent fluid flowing in a flow path with a laser beam from a direction intersecting with the flow, and the transmitted light is received by a light receiving device. In the foreign matter detecting device for detecting the foreign matter in the transparent fluid by converting the electric signal into an electric signal and detecting the foreign matter based on the change in the amount of light received when the foreign matter is mixed in the transparent fluid. Is provided, and the information indicating the size of the foreign matter in the flow direction is corrected based on the velocity information of the foreign matter from the flow velocity detecting means.

[0007]

BEST MODE FOR CARRYING OUT THE INVENTION The present invention can be utilized for detecting foreign matter in a polyethylene material supplied to the above-mentioned cable insulating layer of a power cable or its molded joint portion. Polyethylene resin is milky white translucent at room temperature and has insufficient light transmittance, but becomes transparent when heated and melted when kneading in an extruder, and when foreign matter is mixed in the molten resin. , Can be easily seen through from the outside. Therefore, a transparent flow path made of transparent glass or a resin material is inserted in the middle of the resin flow path connecting the extruder and the crosshead, or between the extruder and the mold, and the laser beam is applied from the outside. The presence or absence of foreign matter and the size of the polyethylene resin that has passed through the inside of the flow channel can be detected by irradiating the light source to detect the change in the amount of received light and subjecting it to signal processing or image processing. When a transmission image of a foreign substance is captured as an electrical signal by scanning with a laser beam, the foreign substance moves in the direction of flow of the polyethylene resin, so the size of the foreign substance is output as a signal of a size different from the actual size in the flow direction. To be done. Further, the distribution of the flow velocity in the polyethylene resin flowing in the transparent channel is not uniform, and is large at the center of the channel and small near the channel wall.
For example, when the inner diameter of the transparent channel is cylindrical and the fluid flowing therethrough complies with Newton's viscosity law, the flow velocity distribution is as shown in the following equation. Become. Ur = K (R ² −r ² ) ……………………………………………… (1) where Ur: Flow velocity at r position K: Constant R: Flow path radius r: Radial Position of Flow Path Polyethylene resin is not a Newtonian fluid that completely complies with the above equation (1), but behaves in a similar manner when the average flow velocity during extrusion is within a predetermined range. Further, when the flow velocity is lower than that, a flow velocity distribution closer to the Bingham fluid is shown, like Vr in FIG. 2B. Therefore,
In the present invention, the transparent fluid is irradiated with a laser beam from a plurality of different positions in the direction of the flow of the transparent fluid,
Each of the transmitted lights is received by a light receiving device and converted into an electric signal, and based on these electric signals, information indicating the presence and size of foreign matter in the transparent fluid is obtained and detected by the plurality of light receiving devices. The velocity information of the foreign matter is calculated from the detected detection time difference of the same foreign matter, and the information indicating the size of the foreign matter in the flow direction is corrected based on the velocity information.

When two sets of laser beam irradiating device and light receiving device are used, since the laser beam irradiating device is generally expensive, a single laser beam irradiating device is used and the laser beam obtained from the laser light source is used. The scanning laser beam reflected by a polygonal rotating mirror such as a polygon mirror is separated into two laser beams through a spectroscopic means including a mirror and a half mirror, and these laser beams are different in the flow direction of the transparent fluid. It is desirable to irradiate the transparent fluid from different positions and receive the transmitted light from the respective light receiving devices. Further, by irradiating the transparent fluid with two laser beams from different positions in the flow direction of the transparent fluid and from a plurality of directions intersecting the flow of the transparent fluid at the same time, the presence / absence of foreign matter and velocity information can be known. Not only is it possible to detect the foreign matter, but also when the foreign matter passes through in an overlapping manner, the overlapping can be identified, so that the number and size of the foreign matter can be accurately obtained.

In the present invention, as a method for determining the flow velocity V of foreign matter in the transparent fluid, the transparent fluid flowing in the flow path is
Imaged with a video camera from a direction intersecting with the flow, the position of the image of the foreign matter on a certain screen, which was captured by this video camera, and the position of the image of the same foreign matter on the subsequently captured screen were compared, The flow velocity V of the foreign matter can also be obtained from the difference between these positions. It should be noted that the flow velocity V of the foreign substance is calculated from the difference in the position of the image of the foreign substance captured by the video camera.
In order to obtain, the transparent fluid flowing in the flow path is scanned with a laser beam from a direction intersecting the flow, the transmitted light is received by a light receiving device and converted into an electric signal, and foreign matter is contained in the transparent fluid. When a foreign substance is detected based on a decrease in the amount of received light that occurs when both are mixed, it is desirable to trigger the capture of the first image. In the present invention, the transparent flow path for irradiating a laser beam or capturing an image with a video camera can be configured by inserting a transparent ring in the middle of the pipeline. In this case, the transparent ring can have a rectangular cross section,
In order not to disturb the flow of the fluid flowing therethrough or cause retention, it is preferable to make it cylindrical with the same inner diameter as the pipeline. In addition, it is desirable that the transparent ring has a refractive index almost equal to that of the transparent fluid passing through it in order to reduce the refraction of the laser beam. Therefore, for example, when the transparent fluid is molten polyethylene, its refractive index is 1.44.
Pyrex glass (refractive index 1.4
It is desirable to configure 7).

[0010]

Next, an embodiment of the present invention will be described with reference to the drawings. FIG. 3 shows the EMJ for the insulating layer of the CV cable described above.
The present invention shows an example in which the present invention is applied to detection of foreign matter in a polyethylene resin supplied to a mold when connecting by a method, and a Pyrex is provided in the middle of the resin supply pipe 1 from the extruder to the mold. A transparent ring 2 made of glass or the like is inserted. The transparent ring has a cylindrical shape having the same inner diameter (about 20 mm) as the pipe line 1, and both upper and lower ends thereof face O-rings 3 between the flanges 4 and 5 on the pipe line side. Further, the flanges 4 and 5 are tightened by bolts and nuts 6 inserted through through holes provided at four places around them, and seal between the flanges 4 and 5 and the transparent ring 2.

On the side of the transparent ring 2, as shown in FIG. 1, a laser beam irradiation device 10 and a half mirror 20 are provided.
And a pair of mirrors 21a and 21b for refracting the laser beams La and Lb split by the half mirrors at right angles in the planes parallel to the paper surface of FIG. 1, and the laser beams La emitted from these mirrors 21a and 21b. , L
A pair of mirrors 22a and 22b (not shown) for refracting b at right angles downward or upward in the axial direction of the transparent ring 2 (direction orthogonal to the paper surface of FIG. 1) and these mirrors 22a and 22b are emitted. A pair of mirrors 23 for refracting the laser beams La and Lb again at right angles in the direction orthogonal to the axis of the transparent ring 2 (in the plane parallel to the paper surface of FIG. 1).
a and 23b, and a pair of light receiving devices 30a and 30b that receive the laser beams La and Lb that have passed through the transparent ring 2 and that have exited these mirrors 23a and 23b.
The half mirror 20 has the laser beams La and Lb halved.
The transmissivity and the reflectivity are selected so that they are split into equal parts, and the mirrors 21a, 21b, 22a, 22b,
23a and 23b are from the half mirror 20 to the light receiving device 30.
a and 30b, the two laser beams La and Lb have equal optical path lengths, the reflectances are equalized so as to have the same attenuation amount, and the laser beams have respective angles of 45 ° with respect to the optical axis of the laser beam. It is accurately positioned. Note that FIG.
Of the two systems of the laser beams La and Lb,
Only the components relating to the laser beam La are shown. In the above, the mirrors 21a, 21b are used to irradiate the laser beams La, Lb from two directions orthogonal to the axis of the transparent ring 2, and the mirrors 22a, 22b, 23a, 23b are shown in FIG. As shown, the laser beams La and Lb are used to pass through the transparent ring 2 at a position separated by an appropriate distance (for example, about 10 mm) in the axial direction.

The digital signals output from the light receiving devices 30a and 30b are processed by the signal processing device 40, and the number of foreign substances, the size in the width direction, the position in the width direction, and the detected flow velocity of the foreign substances and the correction coefficient based thereon. Is calculated and output to the output device 50 and the monitor 60.

As shown in FIG. 4, the laser beam irradiation device 10 includes a laser oscillator 11 made of a semiconductor laser or the like,
A polygon rotary mirror 12 including an octahedral polygon scanner that is driven by a motor (not shown) and rotates at high speed to scan and sweep an incident laser beam, and a laser beam from the polygon rotary mirror 12 A reflection mirror 13 for reflecting the light and a collimator lens (Fθ lens) 1 for converting the incident laser beam into parallel rays.
4 is provided. As shown in FIG. 5, each of the light receiving devices 30a and 30b includes a condenser lens 31, a light receiving element 32 installed at the focal position thereof for converting an optical signal into an analog electric signal, and the analog electric signal into a digital signal. As shown in FIG. 6, a digital signal corresponding to the amount of received light is output to each output terminal 34 as a time-series binary signal. In FIG. 6, the light receiving device output “0”
Means that the laser beam is blocked by the foreign matter, the transmitted light is reduced, and the amount of received light is reduced to a threshold value or less, which means that the foreign matter is present.

The signal processing device 40 includes the light receiving devices 30a and 3a.
When the signal from 0b includes a "0" signal indicating the presence of foreign matter, the number and size of foreign matter are calculated from the number and position. Further, the flow velocity of the foreign substance is obtained from the detection time difference of the same foreign substance by the scanning laser beams La and Lb, and the information indicating the size of the foreign substance in the flow direction is corrected by the correction coefficient calculated based on this flow velocity. The signal processing device 40 has a built-in image processing circuit, and when the input signal includes a "0" signal indicating the presence of a foreign substance, the time series data of the scanning laser beam during that time is stored in the storage device. Stored in a predetermined time series data (for example, scan line 1
(Every 024 pieces) are processed and sent to the monitor 60. This is performed separately for each signal series from the light receiving devices 30a and 30b. As a result, the light receiving devices 30a and 30b are respectively displayed on the monitor screens a and b.
The magnified image of the foreign matter detected by is projected as a slowly moving image. The output device 50 in FIG.
When the output result of the signal processing device 40 is printed and output, and a foreign substance of a size equal to or larger than a predetermined constant value (for example, 100 μm or more when the identification level is several tens of μm) or the number of foreign substances is detected. Outputs an alarm and prompts workers to take measures.

By using the foreign matter detection device having such a configuration,
When detecting foreign matter in the polyethylene resin supplied to the mold when connecting the CV cable by the above-mentioned EMJ method, the cable insulating layer and the semi-conductive layer inside and outside are penciled to expose the exposed cable conductors. A pair of power cables (not shown) connected by a conductor sleeve is assembled with a mold (not shown) around the conductor connecting portion. The polyethylene resin used in the mold is kneaded together with a cross-linking agent in an extruder (not shown), heated and melted into a transparent fluid, which is supplied into the mold through the resin supply pipe 1. When passing through the transparent ring 2 inserted in 1, the laser beam is irradiated and it is inspected whether foreign matter is mixed. That is, the laser beam oscillated from the laser oscillator 11 of the irradiation device 10 is scanned by the polygonal rotating mirror 12 at a frequency of about 600 Hz, and becomes a parallel beam by the collimator lens 14. Note that this scanning is performed in a plane parallel to the paper surfaces of FIGS. The height H of the laser beam to be scanned (the length in the direction orthogonal to the paper surface of FIGS. 1 and 4) is set to about 60 μm. This laser beam is split into two laser beams La and Lb of 50% each through a spectroscopic means such as a half mirror 20, and mirrors 21a, 21b, 22a and 22b, respectively.
The polyethylene resin passing through the transparent ring 2 after being reflected by 23 a and 23 b is irradiated from different positions in the axial direction and the circumferential direction of the transparent ring 2.

At this time, if a foreign substance is mixed in the polyethylene resin, a part of the laser beam is absorbed or scattered by the foreign substance, and the amount of light reaching the light receiving devices 30a and 30b is reduced. The change in the amount of light received by the light receiving devices 30a and 30b is converted into an electric signal by the light receiving element 32, and further converted into a digital signal by the analog / digital conversion device 33 and output. This signal conversion is
As shown in FIG. 6, the scanning is performed for each scanning line and even in the course of scanning, and is divided by a predetermined threshold value.
It is output as a binary signal of "0" or "1". Here, as shown in FIG. 7, the polyethylene resin is flowing from the bottom to the top in the Z-Z 'direction, and the laser beam is scanned in the Y- direction.
Assuming the case where the polyethylene resin mixed with the foreign matter A is passing through in the Y'direction, the foreign matter A has a height H of the scanning line as shown in FIGS. If not, the scan data is all “1” as shown in FIGS. 8A and 8C, but the foreign matter A is within the height H of the scanning line as shown in FIG. 7B. In some cases, the scan data will include "0" as shown in FIG.
It is detected that a foreign object has passed. In this case, the horizontal width of the foreign material A can be obtained from the number of "0" s arranged side by side in the scan data (this is equal to the product of the time width when the amount of received light is reduced and the sweep speed of the scanning line). For example, when the inner diameter of the transparent ring is 20 mm and the scanning speed of the laser beam is 600 Hz, the transit time of the laser beam in the transparent ring is 122.2 μsec (measurement result), and the sampling time is 0.125 μsec. The decomposition number M is M = 122.2 μsec / 0.125 μsec = 978, and the resolution P is P = 20 mm / 978 = 20 μm. Therefore, when the number of “0s” arranged side by side in the scan data is 3, the lateral width W of the foreign matter A is W = 20 μm × 3 = 60 μm.

As described above, the height H of the scanning line is
If the (laser beam spot diameter) is set to about 60 μm and the scanning frequency is set to about 600 Hz, the maximum speed of foreign matter during normal operation (average flow velocity of 7 mm / sec in the above embodiment)
Foreign matter can be reliably irradiated by any of the scanning laser beams even when the foreign matter passes. In other words, since the foreign matter that has reached between the scanning laser beam and the next scanning laser beam is irradiated by the next scanning laser beam, the foreign matter cannot be missed. Foreign body A
If there is no flow, the size in the flow direction can be obtained based on the number of "0" s arranged in the vertical direction in FIG. However, as shown in the above equation (1), etc., the distribution of the flow velocity in the polyethylene resin flowing in the circular channel differs depending on the distance from the central axis of the channel, and flows near the wall surface of the channel. Since the foreign matter has a slow speed and stays within the height H of the scanning line for a long time, the size of the foreign matter A in the flow direction is displayed larger than it actually is.
In addition, foreign matter flowing near the center of the flow path is displayed with a small size in the flow direction. Therefore, in order to know the true size of the foreign matter A in the flow direction, a correction coefficient is obtained from the flow velocity of the foreign matter in the cross section of the transparent fluid, and the size of the foreign matter in the flow direction is calculated based on the correction coefficient. It is necessary to correct the information presented.

In the present invention, the laser beams La, L
Since the transmission position of b is shifted in the axial direction of the transparent ring 2 by about 10 mm, the signal generated when the same foreign matter is detected in the light receiving devices 30a and 30b includes information about the flow velocity of the foreign matter. That is, the light receiving device 3
0a and 30b, the detection time difference when the same foreign matter is first detected is the transmission distance of the laser beams La and Lb (see FIG. 3).
By dividing by S), the flow velocity of the foreign matter can be obtained. In addition, when a plurality of foreign substances pass through the transparent ring 2 at the same time, the foreign substance first detected by the laser beam La has a low flow velocity. Therefore, when passing the laser beam Lb, another foreign substance having a high flow velocity is used. Although it may be detected later, this can be solved by adding a system for discriminating the difference according to the size of the foreign matter.
In the present invention, the true size in the flow direction of the foreign material A can be known by correcting the information indicating the size in the flow direction of the foreign material based on the correction coefficient thus obtained.

As the correction method, the following method can be adopted. (1) When the foreign matter passes at the average flow velocity (V0), the information indicating the size of the foreign matter in the flow direction output from the light receiving devices 30a and 30b is set to be the information indicating the true size of the foreign matter. Then, the correction coefficient C at this time is set to 1. (2) When the passage speed of the foreign matter is higher than the average flow velocity (V0), the information indicating the size of the foreign matter in the flow direction output from the light receiving devices 30a and 30b is output smaller than the true size of the foreign matter. Therefore, in the signal processing device 40, the correction coefficient C1 (>
Correction is performed by multiplying 1). The correction coefficient C1 takes a larger value as the foreign matter passing speed increases. (3) When the passage speed of the foreign matter is smaller than the average flow velocity (V0), the information indicating the size in the flow direction of the foreign matter output from the light receiving devices 30a and 30b is output larger than the true size of the foreign matter. Therefore, in the signal processing device 40, the correction coefficient C2 (<
Correction is performed by multiplying 1). The correction coefficient C2 becomes smaller as the passing speed of the foreign matter becomes smaller. (4) The correction coefficients C1 and C2 are obtained in advance and stored in the storage medium in the signal processing device 40, and are appropriately selected based on the speed information of the foreign matter. For example, the laser beam is 60
When scanning is performed at 0 Hz (= 1.67 msec / scan), as shown in FIG. 9, when four “0” s are continuously arranged in the vertical direction, 1.67 msec / scan × 4 = 6. When the average flow velocity is 7 mm / sec, the apparent size in the flow direction is 6.68 msec × 7 mm / sec = 47 μm, but the measured flow velocity V of the foreign matter is 10 mm / se.
If it is c, the true size L of the foreign matter in the flow direction is 47 μm × 10 mm / 7 mm = 67 μm. Therefore, the correction coefficient C1 in this case is 10 /
It will be 7.

When correcting the information indicating the size of the foreign matter in the flow direction, the above-mentioned multiplication of the correction coefficient is used.
A correction amount determined by the passing speed of the foreign matter may be added to or subtracted from the information indicating the size of the foreign matter in the flow direction.
Further, in the present invention, even when two foreign matters pass through the flow path at the same time, it is discriminated that they are two and their sizes in the X and Y directions by measuring from the orthogonal direction. be able to. FIG. 10 shows the pattern and the foreign matter image on the monitor screens a and b. No. 1 has a spherical foreign substance A in the center of the flow path, and another spherical foreign substance B near the wall surface on the Y-axis (because this foreign substance is near the wall surface, in the longitudinal direction on the monitor screen). It is magnified and looks like an oval.) No. No. 2 shows a pattern in which spherical foreign matters A and B are present in the center of the flow path and near the wall surface on the X axis. 3
Indicates a pattern in which spherical foreign matters A and B are present near the wall surface on the Y axis and the X axis. As described above, in the present embodiment, even when two foreign substances simultaneously pass through the flow path, the number and size of them can be identified, and in general, even when three or more foreign substances are identified, they can be identified. can do.
However, in the unique case where there are three foreign matters, one on the center of the flow path and one on the Y-axis and one on the X-axis, it may not be possible to distinguish them exceptionally. This is because foreign matter images are overlapped on each other and only two images are captured on both the monitor screen a and the monitor screen b. However, since such a case is considered to be extremely rare, there is no problem in practical use.

In the above description, as the flow velocity detecting means, a plurality of light receiving devices are arranged in the direction of flow so as to be separated from each other, and the velocity of the foreign substances can be determined from the detection time difference of the same foreign substances detected by these light receiving devices. Although the example of obtaining information has been described, the flow velocity detecting means in the present invention is not limited to this, and for example, a video camera may be used. In this case, as shown in FIG. 11, only one set of the laser beam irradiation device 10 and the laser receiving device 30 are arranged on both sides of the transparent ring 2, and the video camera 70 and the illumination light are arranged in the direction orthogonal to them. 80 is arranged with the transparent ring 2 sandwiched therebetween.

In FIG. 11, a laser beam irradiation device 1
0 and the light receiving device 30 have the same configurations as those in FIGS. 4 and 5, respectively, and the laser beam output from the laser beam irradiation device 10 traverses the transparent fluid passing through the transparent ring 2. The scanning is done as follows. Further, the transmitted light of the laser beam is detected by the light receiving device 30 and converted into an electric signal. When the amount of received light exceeds the threshold value, “1”, the threshold value, as in the case of FIG. In the following cases, a digital signal of "0" is output.

The signal processing device 40 incorporates a scanning number detecting means and a flow velocity detecting means. The scanning number detecting means processes the digital signal inputted from the light receiving device 30, and as shown in FIG. 9, detects the scanning number N of the laser beam continuously including the “0” signal. The scanning number detecting means 41 issues a signal acquisition command signal toward the flow velocity detecting means while N> 0. The flow velocity detecting means is a video camera 70.
The image signal from the video camera 70 is input and the output is not generated at all times, but when the signal acquisition command signal is received from the scanning number detecting means, the image signal from the video camera 70 is processed to calculate the flow velocity V of the foreign matter. To do. For example, video camera 7
0, the scanning method is a non-interlaced method, 525
This uses a 30-field CCD camera, and its imaging area is 20 mm x 15 which is equal to the inner dimension of the transparent ring 2.
When the shutter speed is set to mm and the shutter speed is set to 10 milliseconds (ms), the time chart of image pickup is as shown in FIG.
Here, the image position of the foreign substance A on the screen at a certain frame (time t = t1) is as shown in FIG. 13 (A), and the foreign substance on the screen at the next frame (time t = t1 +33.3 ms). Assuming that the image position of A is as shown in FIG. 13B, the flow velocity V of the foreign matter can be obtained by dividing the moving distance Dmm between them by the time difference between frames (33.3 ms). If the flow velocity V of the foreign matter is slow, the moving distance between the screens after a certain frame and several frames after that may be divided by the time difference therebetween.

As described above, according to the embodiment of the present invention, when foreign matter is contained in the molten resin, the number and size of the foreign matter can be detected and displayed. In this case, the size of the foreign matter in the flow direction is corrected and displayed as the true size.
Corrective measures can be taken when foreign matter is mixed in. Further, if the laser beam is dispersed using a spectroscopic device including a half mirror, it is not necessary to increase the number of expensive laser beam irradiation devices installed. Further, in the above description, an example in which the present invention is used as a transparent fluid to detect foreign matter in a cable insulating layer of a CV cable or a polyethylene resin used for connecting the same is described, but the present invention is applicable to various types other than polyethylene. It can be widely applied to the inspection of various transparent fluids such as the transparent molten resin material or various transparent fluids that do not like the inclusion of foreign matters such as insulating oil and edible oil. However, the transparent fluid in the present invention does not need to be completely transparent, and if it has such a degree of transparency that a transmission image thereof can be obtained when a foreign substance mixed in the fluid is irradiated with a laser beam. Good. Of course, the present invention can be applied even if the transparent fluid is a gas. Further, in the above embodiment, the example in which the laser beams La and Lb are applied to the transparent fluid from two directions orthogonal to the flow of the transparent fluid has been described, but this need not necessarily be from the orthogonal directions, and depending on the case, It may be from the same direction.

[0025]

According to the present invention, when foreign matter is mixed in the transparent fluid, the size in the flow direction can be accurately detected.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram showing an overall configuration of a working example of the present invention.

FIG. 2 is a graph illustrating a relationship between a radial position of a fluid in a flow path and a flow velocity.

FIG. 3 is an explanatory diagram showing an example in which the present invention is used to detect foreign matter in a polyethylene resin for insulating connection of a power cable.

FIG. 4 is an explanatory diagram showing a configuration example of a laser beam irradiation device according to the present invention.

FIG. 5 is an explanatory diagram showing a configuration example of a light receiving device according to the present invention.

FIG. 6 is a graph illustrating an amount of light received and output data of a light receiving device according to the present invention.

FIG. 7 is an explanatory diagram showing a positional relationship between a scanning line of the light receiving device and a foreign substance in the device of the present invention, along with a change with time.

FIG. 8 is an explanatory view showing a digital signal output from the light receiving device in the device of the present invention along with a change with time.

FIG. 9 is an explanatory diagram showing a digital signal output from the light receiving device in the device of the present invention along with a change with time.

FIG. 10 is an explanatory diagram illustrating three patterns when two foreign matters pass through and a foreign matter image on the monitor screens a and b in the respective patterns in the apparatus of the present invention.

FIG. 11 is an explanatory view showing an embodiment when a video camera is used for detecting the flow velocity of a foreign substance in the present invention.

FIG. 12 is a time chart of imaging in the embodiment of FIG.

13 is an explanatory diagram illustrating the state of an image of a foreign matter in a certain frame and the next frame in the embodiment of FIG.

[Explanation of symbols]

1 ... Pipeline 2 ... Transparent ring 10 ... Laser beam irradiation device 20 ... Half mirrors 21a, 21b, 22a, 22b, 23a, 23b ...
Mirror 30, 30a, 30b ... Light receiving device 40 ... Signal processing device 50 ... Output device 60 ... Monitor 70 ... Video camera.

Claims (7)

[Claims] 1. A transparent fluid flowing in a flow path is irradiated with a laser beam from a direction intersecting the flow, the transmitted light is received by a light receiving device and converted into an electric signal, and foreign matter is contained in the transparent fluid. In a foreign matter detecting device for detecting a foreign matter based on a change in the amount of light received that occurs when mixed, a flow velocity detecting means for detecting the foreign matter in the transparent fluid is provided, and based on the velocity information of the foreign matter from the flow velocity detecting means. A foreign matter detection device in a transparent fluid, characterized in that the information indicating the size of the foreign matter in the flow direction is corrected. 2. A transparent fluid is irradiated with a laser beam from a plurality of positions different from each other in the direction of flow of the transparent fluid, the transmitted light thereof is received by a light receiving device, respectively, and converted into an electrical signal. Based on the information indicating the presence or absence and the size of the foreign matter in the transparent fluid based on, based on the flow velocity detection means, to obtain the speed information of the foreign matter from the detection time difference of the same foreign matter detected by the plurality of light receiving devices, 2. The information indicating the size of the foreign matter in the flow direction is corrected based on the speed information.
The apparatus for detecting foreign matter in a transparent fluid according to item 1. 3. The flow velocity detecting means obtains velocity information of the foreign substance from detection time differences of the same foreign substance detected by a plurality of light receiving devices, obtains a correction coefficient from the velocity information, and the foreign substance is based on the correction coefficient. The foreign matter detection device in the transparent fluid according to claim 2, wherein the information indicating the size in the flow direction is corrected. 4. A laser beam obtained from a single laser light source is reflected by a polygonal rotating mirror, the obtained scanning laser beam is split into two laser beams through a spectroscopic means, and these laser beams are transparent. 4. The foreign matter in the transparent fluid according to claim 1, wherein the transparent fluid is irradiated from two different positions in the flow direction of the fluid, and the transmitted light is received by the light receiving device. Detection device. 5. An apparatus for detecting foreign matter in a transparent fluid according to claim 1, wherein the transparent fluid is irradiated with a laser beam from a plurality of directions intersecting with the flow of the transparent fluid. . 6. An image of a transparent fluid flowing in a flow channel is picked up by a video camera from a direction intersecting with the flow, and an image of a foreign object on a screen, which is picked up by the video camera, and an image after a predetermined time has elapsed. 2. The transparent fluid according to claim 1, wherein the positions of the images of the same foreign matter on the displayed screen are compared with each other, and the flow velocity V of the foreign matter is obtained from the relationship between the positions and the predetermined time. Foreign object detection device. 7. A flow velocity of an image signal is detected from a video camera when a laser beam is scanned on a transparent fluid flowing in a channel and a decrease in the amount of received light caused when foreign matter is mixed in the transparent fluid is detected. The foreign matter detection device in a transparent fluid according to claim 6, wherein the foreign matter flow velocity V of the foreign matter is taken in by the means.