JPH09304413A - Detecting method and equipment for foreign matter in transparent fluid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately detect the presence/absence of foreign matters in transparent fluid and the magnitude in the flow direction, by detecting the flow velocity of foreign matters in transparent fluid and the frequency of scanning of a laser beam wherein the light receiving amount has continuously decreased. SOLUTION: Laser light oscillated from a laser oscillator of an irradiation equipment 10 is scanned by a polygonal rotating mirror, and turned into a parallel ray by a collimator lens. Laser beams La, Lb split by a half-mirror 20 are reflected by mirrors 21a, 21b, 22a, 23b, etc. Polyethylene resin passing a transparent ring 2 is irradiated with the laser beams, from different positions in the axial direction and the circumferential direction of the transparent ring 2. The beams are received by light receiving equipments 30a, 30b. A flow velocity detecting means and a scanning frequency detecting means of a signal processing equipment 40 detect the flow velocity of foreign matters and the scanning frequency of the laser beams wherein the light receiving amount has continuously decreased, and the magnitude of the foreign matters in the flow direction are calculated from the detected values and the scanning period.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a foreign matter detection method and apparatus for detecting the presence and 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. The present invention
When detecting foreign matter with a laser beam,
It is an object of the present invention to provide a method and an apparatus for detecting foreign matter in a fluid, the size of which can be accurately measured.

[0005]

According to a first aspect of the present invention, which relates to a method for detecting foreign matter in a fluid, a transparent fluid flowing in a flow path is scanned with a laser beam from a direction intersecting the flow, and the transparent fluid is transmitted therethrough. A foreign matter in the transparent fluid, wherein the light is received by a light receiving device and converted into an electric signal, and the foreign matter is detected based on a decrease in the amount of light received when the foreign matter is mixed in the transparent fluid. Of the flow velocity V and the number of times N of scanning of the laser beam in which the amount of received light continuously decreases, and based on these detection values and the scanning period T of the laser beam, the size of the foreign matter in the transparent fluid in the flowing direction. Is calculated by the following equation: L = V × N × T ……………………………………………… (1) The invention relates to a transparent fluid that flows in a flow channel and interacts with the flow. The laser beam is scanned from a plurality of directions, and the transmitted light thereof is received by the light receiving device and converted into an electric signal. Based on a decrease in the amount of light received when foreign matter is mixed in the transparent fluid, The size W of the foreign matter in the direction orthogonal to the flow of the transparent fluid is detected, and the flow velocity V of the foreign matter in the transparent fluid is detected.
Then, the number of times N of scanning of the laser beam whose light receiving amount is continuously reduced is detected, and the size L in the flow direction of the foreign matter in the transparent fluid is calculated based on these detection values and the scanning period T of the laser beam. It is characterized by doing.

According to a third aspect of the present invention relating to a foreign matter detecting device in a fluid, a transparent fluid flowing in a channel is scanned 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 detection device, which detects the foreign matter based on a decrease in the amount of received light that occurs when the foreign matter is mixed in the transparent fluid, the flow velocity V of the foreign matter in the transparent fluid is detected. Flow velocity detection means,
The number of scanning times detecting means for detecting the number of times N of scanning of the laser beam whose light receiving amount is continuously decreased, and the flow of foreign matter in the transparent fluid based on the signals from these detecting means and the scanning cycle T of the laser beam. And a size calculating means for calculating the size L in the direction by the formula (1). The fourth invention is a polygonal laser beam obtained from a single laser light source. A laser beam irradiation device that outputs a parallel scanning laser beam that is reflected by a rotating mirror, a spectroscopic unit that disperses the scanning laser beam into two laser beams, and these two dissociated laser beams are transmitted by a transparent fluid. An optical system that irradiates the transparent fluid from different positions in the flow direction and from different directions orthogonal to the flow direction, and the transmitted light of these two laser beams are received respectively to generate electricity. Light receiving devices for converting the signals into signals, processing the signals output from these light receiving devices, the flow velocity V of the foreign matter in the transparent fluid, the number N of times of scanning of the laser beam in which the amount of received light is continuously reduced, and the laser A signal processing device for calculating the size L of the foreign matter in the transparent fluid in the flow direction and the size W in the direction orthogonal to the flow of the foreign matter based on the beam scanning period T, and the signal processing. And an output device for displaying the size of the foreign matter detected based on the output of the device.

[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 electric signal by scanning with a laser beam, the foreign substance moves in the direction of flow of the polyethylene resin, so that the size of the foreign substance differs from the actual size in the direction of flow. It is output as a signal. 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 ) ……………………………………………… (2) where Ur: 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 (2), but exhibits behavior close to that 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 first invention of the present invention (the invention of claim 1), the transparent fluid flowing in the flow path is scanned with a laser beam from a direction intersecting with the flow, and the transmitted light is received by the light receiving device. In the foreign matter detection method of detecting a foreign matter based on a decrease in the amount of light received when the foreign matter is mixed in the transparent fluid, the flow rate V of the foreign matter in the transparent fluid is , The number of times N of scanning of the laser beam in which the amount of received light is continuously decreased is detected, and the size L in the flow direction of the foreign matter in the transparent fluid is calculated based on these detected values and the scanning period T of the laser beam. I am trying. Further, in the second invention of the present invention (the invention of claim 2), the transparent fluid flowing in the flow path is scanned with a laser beam from a plurality of directions intersecting the flow, and the transmitted light thereof is received by the light receiving device. Received by and converted into an electric signal,
The size W of the foreign matter in the direction orthogonal to the flow of the transparent fluid is detected based on the decrease in the amount of light received when the foreign matter is mixed in the transparent fluid, and the flow velocity V of the foreign matter in the transparent fluid is detected. Then, the number of times N of scanning of the laser beam whose light receiving amount is continuously reduced is detected, and the size L in the flow direction of the foreign matter in the transparent fluid is calculated based on these detection values and the scanning period T of the laser beam. I am trying to do it.

In these inventions, as a method for obtaining the flow velocity V of the foreign matter in the transparent fluid, as described in claim 3, laser is applied to the transparent fluid from a plurality of positions different in the direction of the transparent fluid flow. The beam is scanned, the transmitted light is received by the light receiving device and converted into an electric signal, and based on these electric signals, the detection time difference of the same foreign substance detected by the plurality of light receiving devices causes The flow velocity V can be obtained, or as described in claim 5, the transparent fluid flowing in the flow channel is imaged with a video camera from a direction intersecting the flow, and the image is captured with the video camera. Comparing the position of an image of a foreign substance on a screen with the position of an image of the same foreign substance on a screen captured after that, and determining the flow velocity V of the foreign substance from the difference between these positions. It can be. When the flow velocity V of the foreign matter is obtained from the difference in the positions of the images of the foreign matter captured by the video camera, as described in claim 6, the transparent fluid flowing in the flow path has a direction intersecting with the flow. When a foreign substance is detected based on a decrease in the amount of received light that occurs when the transparent fluid scans a laser beam, the transmitted light is received by a light receiving device and converted into an electric signal, and the transparent fluid contains a foreign substance. , It is desirable to apply a trigger to capture the first image.

When two sets of a laser beam irradiation device and a light receiving device are used, the laser beam irradiation device is generally expensive, so a single laser beam irradiation 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, it is possible to know the presence or absence of foreign matter and the flow velocity by irradiating the transparent fluid with two laser beams from different positions in the flowing direction of the transparent fluid and from a plurality of directions intersecting the flow of the transparent fluid at the same time. In addition to the above, the overlapping can be identified even when the foreign substances overlap each other, so that the number and size of the foreign substances can be accurately obtained. In the present invention, the transparent flow path for irradiating the laser beam can be configured by inserting a transparent ring in the middle of the conduit. In this case, the transparent ring may have a quadrangular cross section, but it is preferable that the transparent ring has a cylindrical shape with the same inner diameter as the pipeline so as not to disturb the flow of the fluid flowing therethrough or cause retention. . 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, it is desirable to use Pyrex glass (refractive index 1.47) having a refractive index close to that of 1.44.

[0013]

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 in the signal processing device 40, and the number of foreign matters, the size W in the width direction, the position in the width direction, and the foreign matter based on the detected flow velocity of the foreign matter are detected. The size L in the flow direction 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. Signal processing device 40
Is a flow velocity detecting means for detecting the flow velocity V of the foreign matter in the transparent fluid, a scanning number detecting means for detecting the scanning number N of the laser beam whose light receiving amount is continuously reduced, and signals from these detecting means. A size calculating means for calculating the size L of the foreign matter in the transparent fluid in the flow direction based on the scanning period T of the laser beam by the equation (1) is provided.

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 of foreign matter and the size W in the scanning direction (size in the cross section of the flow channel) are determined from the number and position of the foreign matter. Calculate Further, the number of scanning times N of the laser beam continuously including the “0” signal is detected, and the flow velocity V of the foreign matter is detected from the detection time difference of the same foreign matter by the scanning laser beams La and Lb.
Based on these detected values N and V and the scanning cycle T of the laser beam (reciprocal of the scanning frequency of the laser beam) that has been input in advance, the above equation (1) is calculated to determine the flow direction of the foreign matter. The size L of is output. The signal processing device 40 has a built-in image processing circuit. 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 period is stored. The data is stored in the device, and predetermined time series data (for example, scan line 10
Each time 24 pieces are collected, the image is processed and the monitor 6
Send to 0. This is performed separately for each signal series from the light receiving devices 30a and 30b. As a result, enlarged images of the foreign matter detected by the light receiving devices 30a and 30b are displayed on the monitor screens a and b as slowly moving images. The output device 50 prints and outputs the output result of the signal processing device 40, and outputs an alarm when a foreign substance having a size equal to or larger than a preset fixed value or the number of foreign substances is detected.

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 a case where the polyethylene resin mixed with the foreign matter A is passing through in the Y ′ direction, the foreign matter A has the height of the scanning line as shown in FIGS. When it is not within H (laser beam spot diameter),
As shown in (a) and (c), the scan data are all "1", but when the foreign material A is within the height H of the scanning line as shown in FIG. As in b), the scan data contains "0", and it is detected that the foreign matter has passed. In this case, the size W (horizontal width) of the foreign matter A in the cross-sectional direction is 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) Can be obtained from
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). If 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, if the dimension H (laser beam spot diameter) of the scanning line in the height direction is set to about 60 μm and the scanning frequency is set to about 600 Hz, the maximum speed of foreign matter at the normal time (the above-mentioned execution) In the case of the example, average flow velocity 7m
Even when it passes through at a speed of about m / sec), it is possible to reliably irradiate the foreign matter with any of the scanning laser beams. 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. In this embodiment, since the transmission positions of the laser beams La and Lb are shifted by about 10 mm in the axial direction of the transparent ring 2, the signals generated when detecting the same foreign matter in the light receiving devices 30a and 30b are the foreign matter. Contains information about the flow velocity of. That is, the light receiving devices 30a, 3
The flow velocity of the foreign matter can be obtained by dividing the detection time difference when the same foreign matter is first detected by 0b by the transmission distance of the laser beams La and Lb (S in FIG. 3). Also,
The size L of the foreign matter A in the flow direction can be obtained based on the number of "0" s arranged in the vertical direction in FIG. That is, the number of times N of scanning of the laser beam including the “0” signal continuously is detected, and the scanning laser beams La and Lb are detected.
The flow velocity V of the foreign substance is obtained from the detection time difference of the same foreign substance by the above, and the calculation of the above formula (1) is performed based on these detection values N and V and the scanning cycle T of the laser beam that has been input in advance. The size L in the flow direction of is output. For example, when the scanning laser beams La and Lb are scanning at 600 Hz, the scanning cycle T is T = 1/600 Hz = 1.67 msec / scan, so that the flow velocity V of foreign matter is calculated to be 10 mm / sec, for example. When the number of scanning times N of the laser beam that continuously includes the “0” signal is 4 scan, the size L in the flow direction of the foreign matter is L = 10 mm / sec × 4 scan × 1 from the equation (1). It is detected that 0.67 msec / scan = 67 μm. When a plurality of foreign matters pass through the transparent ring 2 at the same time, the laser beam La
Since the foreign matter first detected by the detector has a low flow velocity, it may be detected later than other foreign substances having a high flow velocity when passing through the laser beam Lb, but this is different depending on the size of the foreign substance. This can be solved by adding a discrimination system.

Further, in the present invention, even when two foreign matters simultaneously pass through the flow path, they are two by measuring from the orthogonal direction, and their sizes in the X and Y directions (width). And size) can be identified. 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, it is enlarged in the flow direction on the monitor screen. , Is reflected in an oval shape.)
There is a pattern. 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 shows 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 the foreign substances can be identified, and in general, even when three or more foreign substances are identified, they can be identified. be able to. 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 cases are considered to be extremely rare,
There is no problem in practical use.

Next, another embodiment of the present invention will be described. FIG. 11 shows an example in which a video camera such as a CCD camera is used to detect the flow velocity V of a foreign substance in a fluid. In this embodiment, a set of a laser beam irradiation device 10 and a light receiving device 30 is used, and the laser beam irradiation device 10 and the light receiving device 30 are arranged so as to face each other on both sides in the same cross section orthogonal to the axis of the transparent ring 2. . Further, a video camera 70 is installed at a position orthogonal to the axis connecting the laser beam irradiation device 10 and the light receiving device 30 and the axis of the transparent ring 2, and images the transparent fluid passing through the transparent ring 2. A light 80 for illumination is arranged on the opposite side of the video camera 70 centering on the transparent ring 2 and illuminates the inside of the transparent ring 2. As the laser beam irradiation device 10 and the light receiving device 30, those having the same configurations as in FIG. 4 and FIG. 5 are used, and the laser beam output from the laser beam irradiation device 10 passes through the transparent ring 2. The transparent fluid is scanned across. 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 includes a scanning number detecting means 4
1, a flow velocity detecting means 42, a calculating means 43, a monitor image signal generating means 44, and a comparing means 45.
The scanning number detecting means 41 processes the digital signal input from the light receiving device 30, and as shown in FIG. 9, the scanning number N (FIG. 9) of the laser beam continuously including the “0” signal.
In the case of, N = 4) is detected. The scanning number detecting means 41 issues a signal acquisition command signal to the flow velocity detecting means 42 while N> 0. The flow velocity detection means 42 receives the image signal from the video camera 70, but does not always output, but is triggered when the signal acquisition command signal is received from the scanning number detection means 41, and the video camera 7
The image signal from 0 is processed, and the flow velocity V of the foreign matter is calculated.
The calculation of the flow velocity V will be described later.

Upon receiving the detection signals of the scanning number N from the scanning number detecting means 41 and the flow velocity V from the flow velocity detecting means 42, the calculating means 43 reads the scanning period T of the laser beam from the laser beam irradiation device 10 and From equation (1),
The size L of the foreign matter in the flow direction is calculated and output. When the image signal generating means 44 receives the output signal of the calculating means 43, the time series data of the scanning laser beam input from the light receiving device 30 is stored in the storage device, and predetermined time series data (for example, the scanning line 1024). Each time (for each book) is accumulated, the image is processed and sent to the monitor 60. As a result, a magnified image of the foreign matter detected by the light receiving device 30 is displayed as a slowly moving image on the CRT screen of the monitor. The output of the calculation means 43 is the comparison means 45.
And the size L of the foreign matter in the flow direction is compared with a predetermined limit value L ′, and if L> L ′, a drive signal is sent to an alarm device 90 such as a buzzer. And to send a stop command signal to the extruder 91,
Stop extrusion of clear fluid. Next, the flow velocity detecting means 4
Calculation of the flow velocity V by 2 will be described. For example, as a video camera, the scanning method is a non-interlace method,
A CCD camera with 525 lines and 30 fields is used, and the image pickup area is 20 mm which is equal to the inner size of the transparent ring 2.
X15mm, shutter speed 10ms (m
In the case of s), the time chart of imaging is as shown in FIG. Here, the image position of the foreign substance A on a certain screen at a certain frame (time t = t1) is as shown in FIG. 13 (A), and the next frame (time t = t1 +33.3 ms).
If the image position of the foreign substance A on the screen is as shown in FIG. 13B, the flow velocity V of the foreign substance can be obtained by dividing the moving distance Dmm between them by the time difference between frames (33.3 ms). You can 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. In this embodiment, one set of laser beam irradiation device 10 is used.
The example using the light receiving device 30 has been described, but as in the case of FIG. 1, the laser beam from the laser beam irradiation device 10 is split by a half mirror or the like, and these are split from the directions orthogonal to each other in the same plane in the transparent ring. By scanning the inside, it is possible to detect the size of the foreign matter in the width or depth direction, and to distinguish the number and the size of two foreign matter even when they simultaneously pass through the flow path. You can

As described above, according to the embodiment of the present invention, when a molten resin contains a foreign substance, the size in the flow direction can be calculated and displayed, and the foreign substance can be displayed if necessary. The width or the size in the depth direction can also be detected. As described above, in the present invention, since the foreign matter is displayed as the true size regardless of the flow velocity thereof, it is possible to properly cope with the countermeasure when the foreign matter is mixed. 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.

In the above description, as the transparent fluid,
An example of using the present invention for detecting foreign substances in a cable insulating layer of a CV cable or a polyethylene resin used for connecting the CV cable has been described. However, the present invention is applicable to various transparent molten resin materials other than polyethylene, insulating oil, and edible oil. It can be widely applied to the inspection of various transparent fluids that do not like foreign matter such as 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 embodiment of FIG. 1, the laser beams La, L
Although the example in which b is irradiated to the transparent fluid from two directions orthogonal to the flow of the transparent fluid has been described, this does not have to be the orthogonal directions, and in some cases, the same direction.

[0027]

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 and a foreign substance of the light receiving device according to the present invention 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 CCD camera is used to detect 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 a 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.

─────────────────────────────────────────────────── ─── Continuation of front page (51) Int.Cl. ⁶ Identification code Office reference number FI technical display location // G01V 8/14 G01V 9/04 B

Claims (9)

[Claims] 1. A transparent fluid flowing in a flow path is scanned with a laser beam from a direction intersecting with 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 detection method for detecting a foreign matter based on a decrease in the amount of received light that occurs when they are mixed, the flow velocity V of the foreign matter in the transparent fluid and the number of scanning times N of the laser beam whose received light amount has continuously decreased Based on the detected values and the scanning period T of the laser beam, the size L of the foreign matter in the transparent fluid in the flow direction is calculated by the following equation: L = V × N × T. …………………………………… (1) A method for detecting foreign matter in transparent fluid, which is characterized in that 2. The transparent fluid flowing in the flow path is scanned with a laser beam from a plurality of directions intersecting with the flow, and the transmitted light thereof is received by a light receiving device to be converted into an electric signal. The size W of the foreign matter in the direction orthogonal to the flow of the transparent fluid is detected based on the decrease in the amount of received light that occurs when foreign matter is mixed in the transparent fluid, and the flow velocity V of the foreign matter in the transparent fluid and the received light are detected. The number N of times of scanning of the laser beam whose amount has continuously decreased is detected, and the size L in the flow direction of the foreign matter in the transparent fluid is calculated based on these detection values and the scanning period T of the laser beam. And a method for detecting foreign matter in a transparent fluid. 3. A transparent fluid is scanned with a laser beam from a plurality of positions different in the direction of the flow of the transparent fluid, the transmitted light thereof is received by a light receiving device, respectively, and converted into an electrical signal. The method for detecting foreign matter in a transparent fluid according to claim 1 or 2, wherein the flow velocity V of the foreign matter is obtained from the detection time difference of the same foreign matter detected by the plurality of light receiving devices based on the above. 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 fluid. 2. The transparent fluid is irradiated from two different positions in the direction of flow of light, and the transmitted light thereof is received by a light receiving device, respectively.
4. The method for detecting foreign matter in a transparent fluid according to any one of items 1 to 3. 5. A transparent fluid flowing in a flow channel is imaged by a video camera from a direction intersecting with the flow, and an image of a foreign object on a screen, which is captured by the video camera, and an image after a predetermined time elapses. 3. The transparent fluid according to claim 1, wherein the positions of the images of the same foreign matter on the displayed screen are compared, and the flow velocity V of the foreign matter is obtained from the relationship between the positions and the predetermined time. Foreign matter detection method inside. 6. 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 flow passage and a decrease in the amount of received light caused when foreign matter is mixed in the transparent fluid is detected. The method for detecting foreign matter in a transparent fluid according to claim 5, characterized in that the flow velocity V of the foreign matter is obtained by taking in the means. 7. A transparent fluid flowing in a channel is scanned with a laser beam from a direction intersecting with 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 decrease in the amount of received light that occurs when mixed, a flow velocity detecting means for detecting a flow velocity V of the foreign substance in the transparent fluid, and a laser in which the amount of received light is continuously reduced. Based on the scanning number detecting means for detecting the scanning number N of the beam and the scanning period T of the laser beam and the signals from these detecting means, the size L in the flow direction of the foreign matter in the transparent fluid is expressed by the following equation L = V × N × T ………………………………………………………………………………………………………………………………………………………………………………………………………………………………………… (1) . 8. A laser beam irradiation device that reflects a laser beam obtained from a single laser light source by a polygonal rotating mirror and outputs a parallel scanning laser beam, and the scanning laser beam is split into two laser beams. And an optical system for irradiating the transparent fluid with these two separated laser beams from different positions in the flow direction of the transparent fluid and from different directions orthogonal to the two directions.
A light-receiving device that receives the transmitted light of each of the two laser beams and converts it into an electric signal, and processes the signals output from these light-receiving devices so that the flow velocity V of the foreign matter in the transparent fluid and the received light amount are continuous. Number of laser beam scans N
And a signal processing device for calculating the size L of the foreign matter in the transparent fluid in the flow direction and the size W in the direction orthogonal to the flow of the foreign matter based on the scanning period T of the laser beam, A foreign matter detection device in a transparent fluid, comprising: an output device that displays the size of the foreign matter detected based on the output of the signal processing device. 9. A video camera for capturing an image of a transparent fluid flowing in a flow channel from a direction intersecting with the flow, a position of an image of a foreign substance on a certain screen captured by the video camera, and an image after that. The foreign matter detection in the transparent fluid according to claim 7, further comprising: a flow velocity calculating unit that compares the positions of the images of the same foreign matter on the screen and obtains the flow velocity V of the foreign matter from the difference between the positions. apparatus.