JP2021162382A - Method and device for inspecting resin pipe fusion joints - Google Patents

Abstract

To provide a method and a device for inspecting resin pipe fusion joints, which enable more accurate and quicker inspection of resin pipe fusion joints.SOLUTION: A method of inspecting resin pipe fusion joints is provided, the method comprising irradiating a resin pipe fusion joint 2 connecting two fusion-bonded resin pipes with a terahertz wave, receiving reflections of the terahertz wave reflecting from the resin pipe fusion joint 2, and evaluating the health of the resin pipe fusion joint 2 according to reception information of the received terahertz wave.SELECTED DRAWING: Figure 3

Description

The present invention relates to an inspection method for inspecting the soundness of a connected state in a resin pipe fusion portion connected by fusing resin pipes to each other, and an inspection device for the resin pipe fusion portion.

For example, resin pipes made of polyethylene or the like are used for pipes for city gas and water services buried underground. As a method for connecting such resin tubes, there are a butt fusion method and an electric fusion method used for a resin tube having a relatively large diameter. The butt fusion method is a method in which the connecting ends of two resin pipes are butt-bonded while being heated and melted. The electric welding method (sometimes referred to as an EF joining method) is a method in which the ends of two resin pipes are inserted into a connecting pipe in which a coiled heating wire is embedded and welded by heating the heating wire.

In the resin pipe fusion part where the resin pipes are fused and connected in this way, when air bubbles are generated inside, or the mud adhering to the surface of the pipe remains as it is inside the resin pipe. There are cases. If there is such an abnormal part inside, there is a risk that a crack will enter from that part, the fused part will be damaged, and gas or tap water will leak out. Therefore, it is necessary to inspect such abnormal parts in a non-destructive state.

Conventionally, as a method for inspecting such an abnormal portion of a fused portion, for example, as described in Patent Document 1, an inspection by ultrasonic flaw detection has been performed. That is, ultrasonic waves are transmitted from the transmitting unit (transmission probe) to the resin tube fusion unit connected by the butt fusion method, and the ultrasonic waves reflected from the resin tube fusion unit are received by the receiving unit (reception probe). (For example, see Patent Document 1).

Japanese Unexamined Patent Publication No. 11-258215

Since the transmission speed of ultrasonic waves differs between the air and the inside of the resin, in the method using ultrasonic waves as in the above conventional configuration, in order to measure accurately, the measuring parts such as the transmitting part and the receiving part are inspected. It must be inspected in contact with the surface of the resin tube. As a result, there is a problem that troublesome work is required and it takes a long time for inspection.

Further, when inspecting the resin pipe fusion portion connected by the butt fusion method as described in Patent Document 1, the butt fusion portion is in a state of protruding outward from the outer peripheral portion of the resin pipe. Therefore, the transmitting unit and the receiving unit are distributed and arranged on both sides of the butt fusion unit, and positioning is performed so that the ultrasonic waves transmitted from the transmitting unit pass through the butt fusion unit and reach the receiving unit. There were disadvantages such as the need for specialized skills and the long inspection time.

An object of the present invention is to provide an inspection method and an inspection apparatus for a resin tube fused portion, which can perform an inspection of the resin tube fused portion with high accuracy and in a short time.

A feature of the method for inspecting a resin pipe fusion portion according to the present invention is that a terahertz wave is applied to the resin pipe fusion portion connected by fusing the resin pipes to each other and reflected from the resin pipe fusion portion. The point is to receive the reflected wave of the incoming terahertz wave and evaluate the soundness of the resin tube fusion portion based on the received information of the received terahertz wave.

According to the present invention, the terahertz wave is used to evaluate the soundness of the resin tube fused portion. Terahertz waves are a type of electromagnetic waves located at the boundary between radio waves and light, and have the properties of radio waves that pass through resin materials, as well as light that has straightness and can be converged by a lens and reflected by a reflector. It has both the properties of.

Therefore, such a terahertz wave is irradiated to the resin tube fusion portion, and the reflected wave reflected from the resin tube fusion portion is received. In the received terahertz wave reception information, not only the reflection from the surface of the resin tube but also, for example, if there is an abnormal part such as air bubbles or foreign matter inside the resin tube, it is reflected from the abnormal part. Therefore, it is possible to determine whether or not an abnormal part exists inside by associating the received information with the passage of time.

As described above, the terahertz wave transmits not only in the air but also inside the resin material like the radio wave, so that the measurement can be performed even if the transmitting part and the receiving part of the terahertz wave are separated from the resin tube. There is no need to perform measurement work while in contact with the pipe, and work can be performed efficiently. Moreover, the measurement accuracy does not decrease.

Therefore, it has become possible to provide an inspection method for the resin pipe fusion portion, which can perform the inspection for the resin pipe fusion portion with high accuracy and in a short time.

In the present invention, it is preferable to converge the terahertz wave and irradiate the detected portion in the resin tube fusion portion with a small diameter irradiation range.

According to this configuration, since the terahertz wave is irradiated in a small diameter irradiation range, even if a small defect exists as an abnormal part inside the resin tube, the defect can be detected accurately. It becomes.

In the present invention, it is preferable that the diameter of the terahertz wave applied to the detected portion is about 1 mm to several mm.

According to this configuration, it is assumed that the size of the abnormal portion that may cause a decrease in the strength of the resin pipe fused portion is smaller than, for example, a size of about several mm. Therefore, if the diameter of the terahertz wave is set to about 1 mm to several mm, for example, in the case of creating a tomographic image in order to make it easier to discriminate an abnormal portion having the above-mentioned size. For example, it is possible to make the obtained image as clear as possible without blurring and to detect it with high accuracy.

In the present invention, it is preferable to irradiate a pulsed terahertz wave having a frequency of 0.1 to 2.5 THz (terahertz).

According to the applicant's experiment, if a terahertz wave in a frequency band lower than the above frequency band is used, it may not be possible to detect it unless the defect is larger. Further, if a terahertz wave having a frequency band higher than the above frequency band is used, the reflected wave becomes small due to the influence of the shape of the resin tube fusion portion, and there is a possibility that the inspection based on the received wave cannot be performed accurately.

According to experiments, the applicant uses a pulsed terahertz wave containing a frequency of 0.1 to 2.5 THz (terahertz), and the size of the abnormal portion inside the resin tube is, for example, about 0.5 mm. It has been found that it is possible to accurately detect defects and the like having a size of about several mm. In addition, by using a pulsed terahertz wave, it is easy to manage the correlation between the passage of time and the signal of the reflected wave corresponding to the abnormal part, and it is possible to accurately detect the abnormal part inside the resin tube. be.

In the present invention, a terahertz wave is applied to the detected portion of the resin tube fusion portion in a direction orthogonal to the surface of the resin tube, and the detected portion is directed to the surface of the resin tube. It is preferable to receive terahertz waves reflected in orthogonal directions.

According to this configuration, the terahertz wave is irradiated in the direction orthogonal to the surface of the resin tube, and the terahertz wave reflected in the direction opposite to that direction is received, so that the transmitting unit that transmits the terahertz wave and the reflected wave are received. It is possible to store them compactly by providing the receiving units in close proximity to each other or by providing them in the same housing.

In the present invention, a tomographic image of the resin tube fusion portion is created from the received information of the terahertz wave, and further, the resin tube is based on the image information obtained by performing wavelet transform on the tomographic image. It is preferable to determine the abnormal portion in the fused portion.

According to this configuration, for example, like an ultrasonic diagnostic apparatus, reception information such as an echo of a terahertz wave, for example, the elapsed time from the transmission of the terahertz wave to the reflection and reception, and the reflection. Create a tomographic image of the resin pipe fusion part from the received signal of the terahertz wave. In the tomographic image obtained in this way, it is common to use the Fourier transform as a method for emphasizing the abnormal part. In this method, the frequency information of the received signal can be obtained, but the time information is lost. It is said. When a pulsed terahertz wave is used, if the time information is lost, there is a disadvantage that the resolution over time and the frequency resolution cannot be compatible with each other.

Therefore, based on the image information obtained by performing the wavelet transform on the tomographic image, the abnormal portion in the resin tube fusion portion is determined. The wavelet transform can be changed so as to emphasize the signal corresponding to the abnormal portion by extracting a specific frequency component from the received signal having the time information. As a result, it is possible to accurately determine the abnormal portion in the resin tube fusion portion while achieving both the time-lapse resolution and the frequency resolution.

The features of the inspection device for the resin tube fusion section according to the present invention are an irradiation section that irradiates a terahertz wave to the resin tube fusion section that is connected by fusing the resin tubes to each other, and the resin tube fusion section. It is provided with a receiving unit that receives the reflected terahertz wave reflected from the resin tube and an evaluation processing unit that evaluates the soundness of the resin tube fusion unit based on the received terahertz wave reception information. At the point.

According to this configuration, the irradiation unit irradiates the resin tube fusion portion with a terahertz wave. The receiving unit receives the reflected wave reflected from the resin tube fusion unit. The evaluation processing unit tells that the received information of the terahertz wave includes not only the reflection from the surface of the resin tube but also an abnormal part such as air bubbles or foreign matter inside the resin tube. Is also reflected, so it is evaluated whether or not there is an abnormal part inside, that is, whether or not the resin pipe fusion part is soundly connected, by associating the received information with the passage of time. ..

Terahertz waves are a type of electromagnetic waves located at the boundary between radio waves and light, and have the properties of both radio waves and light. That is, it has the property of a radio wave transmitted through a resin material, has straightness, is reflected on the surface of an object, can be converged by a lens, and has the property of light. In this way, the terahertz wave penetrates not only in the air but also inside the resin material like radio waves, so it is possible to measure even if the transmitting part and receiving part of the terahertz wave are separated from the resin tube, and the resin tube. There is no need to perform measurement work while in contact with the plastic, and work can be performed efficiently. Moreover, the inspection accuracy does not decrease.

Therefore, it has become possible to provide an inspection device for the resin pipe fusion part, which can perform the inspection for the resin tube fusion part with high accuracy and in a short time.

It is a front view of the inspection apparatus of a resin pipe fusion part. It is a side view of the inspection apparatus of a resin pipe fusion part. It is a side view of the inspection head part. It is a control block diagram. It is a figure which shows the received data. It is sectional drawing which shows the measurement principle. It is a figure which shows the tomographic image. It is sectional drawing of the resin tube fusion part by the electric fusion method. It is a figure which shows the received data. It is a figure which shows the tomographic image. It is a figure which shows the data of the wavelet transform. It is a figure which shows the image after conversion.

Embodiments of the present invention will be described with reference to the drawings.
1 and 2 show an inspection device for carrying out the inspection method for the resin tube fused portion according to the present invention. This inspection device is for inspecting the soundness of the resin tube fusion section 2 in which the resin tubes 1 made of a synthetic resin material such as polyethylene are fused to each other by the butt fusion method. The resin pipe fusion portion 2 is formed by abutting the rear end of one resin pipe 1 and the front end of the other resin pipe 1 and crimping them while heating and melting.

As shown in FIG. 1, this inspection device irradiates the resin tube fusion section 2 with a terahertz wave and receives the reflected wave of the terahertz wave reflected from the resin tube fusion section 2. A head portion 3 for inspection and a head support device 4 for supporting the head portion 3 for inspection are provided.

This inspection device irradiates the resin tube fusion section 2 with a terahertz wave, receives the reflected terahertz wave reflected from the resin tube fusion section 2, and uses the received terahertz wave reception information as the received information. Based on this, it is a device for evaluating the soundness of the resin tube fusion section 2.

As shown in FIG. 3, the inspection head unit 3 includes an irradiation unit 5 that irradiates a detected portion of the resin tube fusion unit 2 with a terahertz wave in a direction orthogonal to the surface of the resin tube 1. The receiving unit 6 that receives the terahertz wave reflected from the detected portion in the direction orthogonal to the surface of the resin tube 1 is housed in the same housing 3A. The irradiation unit 5 irradiates a pulsed terahertz wave (hereinafter, referred to as a terahertz pulse wave) including a frequency of 0.1 to 2.5 THz (terahertz).

Further, the inspection head unit 3 has a lens 7 that converges the terahertz wave emitted from the irradiation unit 5 and the reflected terahertz wave, and a receiver unit 6 reflects a part of the reflected terahertz wave. A beam splitter 8 for guiding is provided. The terahertz wave irradiated from the irradiation unit 5 is converged by the lens 7 so as to form a spot portion having a small diameter. The diameter of the spot portion of the terahertz wave irradiated to the detected portion is preferably about 1 mm to several mm.

The head support device 4 supports the inspection head portion 3 so that the position can be changed in the circumferential direction and the axial direction of the resin tube 1 and the separation distance in the radial direction from the resin tube 1 can be changed. It is configured as follows. That is, the head support device 4 is supported by a circular support 9 that is located on the radial outer side of the resin tube 1, extends over the entire circumference, and can be divided into a plurality of units along the circumferential direction. The position of the inspection head 3 is changed along the radial direction with respect to the body 9, and the relative position of the inspection head 3 is changed along the circumferential direction with respect to the support 9 and the radial position adjusting mechanism T3. The circumferential position adjusting mechanism T2 that supports the resin tube 1 and the support 9 with respect to the resin tube 1 are adjustable and the radial distance between the resin tube 1 and the support 9 is maintained constant. A shaft-core direction position adjusting mechanism T1 that supports the resin tube 1 and the support 9 in a state where the position can be changed and adjusted along the shaft-core direction and the radial separation distance between the resin tube 1 and the support 9 is kept constant. I have. Hereinafter, a specific configuration will be described.

The head support device 4 is provided with a circular support 9 that is located on the radial outer side of the resin tube 1, extends over the entire circumference, and can be divided into a plurality of units along the circumferential direction. .. Two supports 9 are provided so as to be separated from each other in the axial direction of the resin tube 1. The two supports 9 are integrally connected by four connecting rods 10 provided at intervals in the circumferential direction.

Each of the four connecting rods 10 is provided with two sets of rolling rollers 11 at intervals in the longitudinal direction. The rolling roller 11 is rotatably supported around the axis along the tangential direction of the outer peripheral surface of the resin pipe 1 by the support bracket 12 fixed to the connecting rod 10. The plurality of rolling rollers 11 are provided so as to be in contact with the outer peripheral surface of the resin pipe 1 and to be movable along the axis direction while rolling on the outer peripheral surface.

In this way, the support 9 is supported in a state where a plurality of rolling rollers 11 provided at intervals in the circumferential direction are in contact with the outer peripheral portion of the resin pipe 1, and therefore, between the support 9 and the resin pipe 1. The radial spacing of the is always kept constant. The rolling roller 11 of any of the plurality of rolling rollers 11 is provided with a shaft-core direction drive motor 13, and the rolling roller 11 is rotated by the shaft-core direction drive motor 13 to rotate the rolling roller 11 to make the inspection head portion 3. The entire head support device 4 including the head support device 4 is supported so as to be repositionable in the axial direction of the resin tube 1. As the axial drive motor 13, a servomotor capable of controlling the rotation speed and the rotation angle is used. The shaft-core direction position adjusting mechanism T1 is configured by the support structure of the support 9 by the plurality of rolling rollers 11 and the shaft-core direction drive motor 13.

The support 9 is configured so that it can be attached to and detached from the outer peripheral portion of the long resin tube 1. That is, it is divided into two in the circumferential direction, and at one of the divisions, it is swingably connected by a hinge 14 around the axis X parallel to the axis direction of the resin tube 1, and the other division can be connected and disconnected. It is connected by a connecting device 15.

The inspection head portion 3 is supported so that its relative position can be changed and adjusted along the circumferential direction with respect to one of the supports 9, and the position can be changed and adjusted along the radial direction with respect to the support 9. As shown in FIG. 2, a base portion 16 that is movably supported in the circumferential direction is provided with respect to the support body 9, and the inspection head portion 3 is a resin tube 1 with respect to the base portion 16. It is supported so that it can move relative to the radial direction of. A guide rail portion 17 for guiding the base portion 16 in the circumferential direction is formed on each of the outer peripheral portion and the inner peripheral portion of the support body 9.

The base portion 16 is provided with four guide wheel bodies 18 that can rotate while sandwiching the support 9 from both inside and outside, and one of them is rotationally driven to drive the base portion 16 in the circumferential direction of the resin tube 1. A circumferential drive motor 19 that can be moved along the line is provided. Each guide wheel body 18 is provided with locking collars 20 on both the left and right sides so as to be movable in the circumferential direction while preventing the guide wheels from coming off. On the outer peripheral portion of the guide wheel body 18 driven by the circumferential drive motor 19, the base portion 16 is engaged with the support body 9 while engaging with a rack gear portion (not shown) provided on the outer peripheral portion of the support body 9. A gear portion (not shown) for guiding in the circumferential direction is formed. Although not described in detail, the gear portion and the rack gear portion are gears having a fine pitch, so that the position can be adjusted in the circumferential direction with high accuracy.

As the circumferential drive motor 19, it is preferable to use a servomotor capable of controlling the rotation speed and the rotation angle. A circumferential position adjusting mechanism T2 is configured by a support structure that movably supports the base portion 16 in the circumferential direction and a circumferential drive motor 19.

Between the base portion 16 and the inspection head portion 3, for example, a slide operation mechanism 21 using a rack gear and a pinion gear, and a radial drive motor 22 for driving and operating the slide operation mechanism 21 are provided, and the radial drive motor 22 is provided. By the operation of 22, the inspection head portion 3 can be moved and operated in the radial direction with respect to the base portion 16. That is, the slide operation mechanism 21 and the radial drive motor 22 constitute the radial position adjusting mechanism T3. As the radial drive motor, it is preferable to use a servomotor capable of controlling the rotation speed and the rotation angle.

The rolling roller 11 holds the radial position of the base portion 16 with respect to the support 9 at a fixed position. The diameter of the base portion 16 with respect to the support 9 is maintained by the radial position holding structure, the support structure for supporting the inspection head portion 3 to the base portion 16 in the radial direction, and the radial drive motor 22. The directional position adjusting mechanism T3 is configured.

As shown in FIG. 4, the inspection device includes an optical pulse generating unit 23 that generates an optical pulse given to the inspection head unit 3 in order to generate a pulsed terahertz wave having a pulse width of an extremely short time. , Each drive motor of the optical pulse generation unit 23, the inspection head unit 3 and the head support device 4 is controlled, and the soundness of the resin tube fusion unit 2 is evaluated based on the received terahertz wave reception information. A control unit 24 as an evaluation processing unit is provided.

The control unit 24 processes the output signals output from the motor control unit 25 that controls the operation of the axial drive motor 13, the circumferential drive motor 19, and the radial drive motor 22 and the inspection head unit 3. A signal processing unit 26 for processing and an image display unit 27 for displaying image information obtained by signal processing are provided. Although detailed control is omitted, the motor control unit 25 scans the inspection head unit 3 along the axis direction by the axial drive motor 13 and the inspection head unit by the circumferential drive motor 19. 3 is controlled to be scanned along the circumferential direction. Further, the radial drive motor 22 is controlled to change the radial position of the inspection head portion 3.

The optical pulse generation unit 23 includes a laser transmission unit 28 having a femtosecond laser, a beam splitter 29 that divides the laser transmitted from the laser transmission unit 28 into two systems, and an optical delay unit 30 that delays the probe light. There is. The laser emitting unit 28 can repeatedly output pulsed laser light having an extremely short pulse width of ^{femtoseconds (1 × 10 -15) seconds.}

The laser light emitted from the laser transmitting unit 28 is divided into pump light and probe light by the beam splitter 29. The pump light is transmitted to the irradiation unit 5 of the inspection head unit 3 via the optical cable 31 and is used as a trigger for the irradiation timing. The probe light is transmitted to the receiving unit 6 of the inspection head unit 3 in a state of being delayed for a predetermined time via the optical delay unit 30 and the optical cable 32, and is used as a trigger for the reception timing.

After the terahertz pulse wave is irradiated by the irradiating unit 5, the light pulse is supplied from the irradiating unit 5 with a delay corresponding to the elapsed time until it is reflected and received by the receiving unit 6. The timing of irradiating the pulse wave and the timing of reflecting the terahertz pulse wave at the inspection target location are combined to determine the reception timing of the reflected wave received by the receiving unit 6 and the receiving timing of the pulse delayed by the optical delay unit 30. Matching. Terahertz time region spectroscopy, which is a well-known technique, is used to enable accurate measurement. The delay time in the optical delay unit 30 can be changed and adjusted.

The motor control unit 25 sets the inspection head unit 3 at a set position for measurement, that is, a position where the resin tube fusion unit 2 can irradiate a terahertz pulse wave, and sets the irradiation position in the circumferential direction. In addition, the axis direction drive motor 13 and the circumferential direction drive motor 19 are controlled so that the receiving unit 6 sequentially measures while scanning in the axis direction. Further, the radial drive motor 22 is controlled so that the spot portion of the terahertz wave is changed along the thickness direction (diameter direction) of the resin tube 1.

Since the signal processing unit 26 has a well-known configuration, it will not be described in detail, but signal processing can be performed based on the received information corresponding to the passage of time obtained by the receiving unit 6 of the inspection head unit 3, for example, FIG. As shown in No. 7, it is configured to obtain information on a tomographic image similar to that of a conventional ultrasonic sonar. The image display unit 27 displays a tomographic image obtained by the signal processing unit 26.

If the support 9 is connected by the hinge 14 as described above, the inspection head portion 3 cannot be moved in the circumferential direction over the entire circumference of the support 9, but for example, the inspection head portion 3 may be replaced, or two inspection head portions 3 may be provided, and it is preferable that the inspection can be performed over the entire circumference.

Next, an inspection method for evaluating the soundness of the resin pipe fusion portion 2 using the above inspection device will be described.

As shown in FIG. 3, a terahertz pulse wave is emitted from the irradiation unit 5 to the detected portion of the resin tube fusion unit 2 in the direction orthogonal to the surface of the resin tube 1, that is, in the radial direction of the resin tube 1. Irradiate toward. At this time, the terahertz pulse wave is converged by the lens 7 and irradiated to the detected portion in the resin tube fusion portion 2 in the irradiation range having a small diameter. The spot diameter of the terahertz pulse wave applied to the detected portion is set to be approximately 1 mm. Then, the terahertz pulse wave reflected from the detected portion in the direction (diameter direction) orthogonal to the surface of the resin tube 1 is received by the receiving unit 6 via the beam splitter 29. The applicant has selected a terahertz pulse wave containing a frequency of 0.1 to 2.5 THz as a frequency band as the terahertz wave emitted from the irradiation unit 5. The terahertz pulse wave is adjusted so that the number of pulses is repeatedly generated so that measurement data for about 1000 times per second can be obtained. The scanning speed of the inspection head unit 3 is set to 100 mm / sec.

Considering the wavelength corresponding to the frequency of electromagnetic waves, a terahertz wave with a frequency of 0.1 THz is suitable for inspection of an abnormal part having a size of about 3 mm, and a terahertz wave with a frequency of 1 THz has a size of about 0.3 mm. Suitable for inspection of abnormal parts. Further, a terahertz wave having a frequency of 2 THz is suitable for inspection of an abnormal portion having a size of about 0.15 mm.

5 and 6 show a measurement principle for inspecting an abnormal portion such as an internal defect of the resin tube fusion portion 2 due to the terahertz pulse wave. When the terahertz pulse wave is applied to the resin tube 1, the terahertz pulse wave passes from the surface of the resin tube 1 through the inside to the lower surface. Since the terahertz pulse wave also has the property of light, it is reflected at the boundary surface and the place where the state is different. Therefore, the resin tube 1 is strongly reflected by the outer surface 1a and the inner surface 1b (see A and B in FIG. 6). If an abnormal portion α such as a bubble or a foreign substance exists inside the resin tube 1, the terahertz pulse wave is strongly reflected at that portion α (see C in FIG. 6).

FIG. 5 shows the waveform of the received signal with the passage of time for the irradiated terahertz pulse wave. The first waveform "A" indicates the received signal reflected on the outer surface 1a, and the second waveform "B" indicates the received signal reflected on the inner surface. The third waveform “C” indicates the received signal reflected at the internal abnormal portion α.

By receiving the reflected terahertz pulse wave in the receiving unit 6 and processing the signal by the signal processing unit 26, for example, a tomographic image as shown in FIG. 7 is created and displayed on the image display unit 27. .. FIG. 7 shows the actual measurement data of the applicant, and shows a tomographic image of a portion of the resin tube fusion portion 2 irradiated with the terahertz pulse wave. In this figure, the horizontal direction corresponds to the position in the circumferential direction of the resin pipe 1, and the vertical direction corresponds to the position in the radial direction (thickness direction) of the resin pipe fusion portion 2.

In FIG. 7, it can be seen that the region on the left side has no abnormal portion inside, and the region on the right side has an arc-shaped abnormal portion α in the middle portion. In this way, it was possible to visually determine that there was an abnormality inside the resin pipe fusion portion 2. The abnormal part used in this experiment is a cavity having a diameter of 0.5 mm.

Therefore, the soundness of the resin pipe fusion unit 2 can be evaluated based on the tomographic image created by processing the signal obtained by the reception unit 6.

In order to accurately detect a small abnormal portion of about 0.5 mm, it is preferable to change the irradiation range (1 mm diameter) having a small diameter converged by the lens 7 in the radial direction with respect to the resin tube fusion portion 2. .. Therefore, it is preferable to move the inspection head portion 3 along the radial direction of the resin tube 1, for example, by 3 mm, and perform measurement while scanning at each position in the circumferential direction and the axial center direction. In this case, the delay time by the optical delay unit 30 may be changed and adjusted.

In the above-mentioned inspection method, the resin tube fusion portion 2 in which the resin tube 1 is fused by the butt fusion method is targeted, but the resin tube in which the resin tube is fused by the electric fusion method (EF joining method) is targeted. It can also be used for the fused portion 2.

FIG. 8 shows a cross section of the resin pipe fusion portion 2 by the electric fusion method. In the resin pipe fusion portion 2 by the electric fusion method, a resin connection pipe 41 in which a coil-shaped heating wire 40 is embedded is externally inserted across the ends of the two resin pipes 1 and heated by the heating wire 40. The resin pipe 1 and the connecting pipe 41 are melted and fused.

The resin pipe fusion portion 2 by the electric fusion method can be inspected by using the above-mentioned inspection device. In the inspection of the resin tube fusion portion 2 by this electric fusion method, since the fusion range is long in the axial core direction, it is necessary to take a long movable range in the axial core direction of the inspection head portion 3. Other than that, the same inspection method as the above-mentioned inspection method can be used.

9 to 12 show actual measurement data of the applicant. FIG. 9 shows a waveform of intensity that changes with the passage of time of the reflected wave reflected from the irradiated terahertz pulse wave, and FIG. 10 shows a tomographic image. In the data D that changes significantly in FIG. 9 and the tomographic image, the location β where there is an intermittently strong output on the upper side indicates the location where the heating wire 40 exists. Further, an abnormal portion γ such as a bubble is shown near the portion β of the heating wire 40. In FIG. 9, it is represented by a small variation data E. However, in the tomographic image, the ghost signal of the surface reflected wave of the terahertz wave and the reflected wave from the abnormal part overlap, and it may be difficult to determine the abnormal part from the image.

In the inspection of the resin tube fusion section 2 by bad fusion, the soundness of the resin tube fusion section 2 is evaluated based on the tomographic image created by processing the signal obtained by the reception section 6. However, in the inspection of the resin tube fusion section 2 by the electric fusion method, the image information obtained by performing wavelet transform on the tomographic image created by processing the signal obtained by the receiver 6 was obtained. Based on this, the abnormal portion in the resin pipe fusion portion 2 was determined.

Although detailed description is omitted because it is a well-known technique, wavelet transform is a procedure for performing data conversion so as to emphasize the reflected wave from an abnormal portion by extracting a specific frequency component.

For example, a process of extracting a component of a specific frequency (for example, 0.4 THz) from the output waveform shown in FIG. 9, obtaining a component of a specific frequency corresponding to the passage of time as shown in FIG. 10, and emphasizing the output is performed. Then, a new tomographic image as shown in FIG. 12 is obtained. With this tomographic image, the shadow due to the ghost signal disappears, and only the abnormal part γ is emphasized, making it easy to understand. In the drawings attached to the specification, the light and darkness of the abnormal portion γ is not clear in some cases, but it is in a state where it can be recognized by the data of the applicant.

[Another Embodiment]
(1) In the above embodiment, the spot diameter of the terahertz wave applied to the detected portion is approximately 1 mm, and it may be about 1 to several mm in order to inspect a small abnormal portion of 1 mm or less. However, the spot diameter of the terahertz wave may be set smaller than 1 mm or larger than several mm depending on the size of the abnormal portion to be inspected and the like.

(2) In the above embodiment, a pulsed terahertz wave including a frequency of 0.1 to 2.5 THz (terahertz) is irradiated, but the abnormality portion to be inspected is not limited to such a peripheral frequency band. Depending on the magnitude and the like, a frequency lower than 0.1 THz may be used, or a terahertz wave having a frequency higher than 2.5 THz may be used.

(3) In the above embodiment, the terahertz wave is irradiated in the direction orthogonal to the surface of the resin tube 1, and the terahertz wave reflected from the detected portion in the direction orthogonal to the surface of the resin tube 1 is received. However, instead of such a configuration, the following configuration may be used. That is, the irradiation portion 5 is arranged on one side of the resin tube 1 in the axial core direction with respect to the resin pipe fusion portion 2, and the receiving portion 5 is received on the other side of the resin pipe 1 in the axial core direction with respect to the resin pipe fusion portion 2. The portion may be arranged to irradiate the surface of the resin tube 1 with a terahertz wave in an oblique direction and receive the reflected wave reflected in the oblique direction.

(4) In the above embodiment, the scanning speed of the inspection head portion 3 is set to 100 mm / sec, but the scanning speed is not limited to this value, and the difference in the size of the abnormal portion to be detected and the inspection are necessary. It may be changed as appropriate according to the difference in time and the like.

The configuration disclosed in the above embodiment (including another embodiment, the same shall apply hereinafter) can be applied in combination with the configuration disclosed in other embodiments as long as there is no contradiction. , The embodiments disclosed in the present specification are examples, and the embodiments of the present invention are not limited thereto, and can be appropriately modified without departing from the object of the present invention.

INDUSTRIAL APPLICABILITY The present invention can be applied to an inspection method for inspecting the soundness of a connected state in a resin tube fusion portion in which resin tubes are fused and connected to each other.

1 Resin pipe 2 Fat pipe fusion part 5 Irradiation part 6 Receiver part 24 Evaluation processing part

Claims (7)

The terahertz wave is irradiated to the resin tube fusion part connected by fusing the resin tubes to each other, the reflected wave of the terahertz wave reflected from the resin tube fusion part is received, and the received terahertz wave is received. A method for inspecting a resin tube fused portion for evaluating the soundness of the resin tube fused portion based on wave reception information. The method for inspecting a resin tube fused portion according to claim 1, wherein the terahertz wave is converged and the detected portion in the resin tube fused portion is irradiated in an irradiation range having a small diameter. The method for inspecting a resin tube fused portion according to claim 2, wherein the diameter of the terahertz wave applied to the detected portion is about 1 mm to several mm. The method for inspecting a resin tube fused portion according to any one of claims 1 to 3, wherein a pulsed terahertz wave including a frequency of 0.1 to 2.5 THz (terahertz) is irradiated. A terahertz wave is applied to the detected portion of the resin tube fusion portion in a direction orthogonal to the surface of the resin tube, and reflected from the detected portion in a direction orthogonal to the surface of the resin tube. The method for inspecting a resin tube fused portion according to any one of claims 1 to 4, which receives a terahertz wave. An abnormality in the resin tube fusion section is created based on the image information obtained by creating a tomographic image in the resin tube fusion section from the received information of the terahertz wave and further performing wavelet transform on the tomographic image. The method for inspecting a resin pipe fused portion according to any one of claims 1 to 5, wherein the location is determined. An irradiation unit that irradiates a terahertz wave to a resin tube fusion portion connected by fusing resin tubes to each other, and a receiver that receives a reflected wave of the terahertz wave reflected from the resin tube fusion portion. An inspection device for a resin tube fusion section, comprising an evaluation processing section for evaluating the soundness of the resin tube fusion section based on the received terahertz wave reception information.

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