JP3535682B2 - Prevention method of multiple reflections in pipes in ultrasonic inspection system - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for preventing multiple reflection inside a pipe in a system for investigating the inside of a pipe such as a buried pipe by utilizing sound waves.

[0002]

2. Description of the Related Art Pipes such as gas pipes and water pipes buried in the ground may be corroded and deteriorated by laying for a long period of time or damaged by external force. Therefore, it is necessary to investigate the inside of the pipe and take repair measures by repair work. Conventionally, as one of the systems used for investigating the inside of this kind of pipeline, there is a system in which a device such as a camera or a fiberscope is inserted into the pipeline so that the state inside the pipeline can be directly viewed. However, the method of inserting such a device requires additional equipment such as a cable to be inserted into the pipeline and insertion work, which may result in a large amount of work and equipment for investigation. Further, if there is a breakage point or a branch point in the middle of the pipeline, it is difficult to guide the equipment at that location, which causes a problem that the entire pipeline cannot be accurately investigated. Therefore, instead of such a method, a system is proposed in which a sound wave is sent from the end of the pipeline and the state of reflection of the sound wave is observed to simply check the situation inside the pipeline from both ends or one end of the pipeline. (For example, JP-A-61-29757 and JP-A-61-202158). In the above-mentioned publication, a sounding means and a sound collecting means are arranged at the end of the conduit, and it is detected that the sound wave sent from the sounding means is reflected at the cross-sectional area change portion generated in the conduit, and the cross-sectional area is detected. A technique capable of observing the position up to the changed portion is disclosed. Such a technique can not only detect the cross-sectional area changing portion in the pipe but also investigate the position of the joint portion or the like installed in the pipe by observing the generation position of the reflected sound wave.

[0003]

However, in the case of investigating the inside of a conduit by using sound waves, multiple reflection occurs in the sound waves sent from the sounding means, and a sound wave signal due to the multiple reflection is observed. However, there is a risk that the signal may be erroneously determined to be from a reflection source inside the tube. Multiple reflection mainly occurs between the branching part or the end part located in the pipe and the sounding means, and at a timing unrelated to the reflection signal from the regular installation position such as the joint part located in the pipe. Therefore, there is a case where it is erroneously determined that the member serving as the reflection source exists in the tube, even though the tube does not exist in the tube.

4A and 4B are views for explaining a case where multiple reflection occurs in a pipeline, where FIG. 4A shows a piping path, and FIG. 4B shows a pipeline path shown in FIG. The reception timing of the reflected sound wave is shown. FIG. 4 (A) shows an example of determining whether or not a reflection source such as a joint exists in a pipe for a pipe line where no branch pipe exists between one end and the other end in the laying direction. A speaker 1 corresponding to a sound generating means and a microphone 2 corresponding to a sound collecting means are arranged at one end of the path S. When a pulsed sound wave is transmitted from the sounding means 1 in the pipe line S, the other end of the pipe line S is reflected as a reflection source and reflected by the microphone 2 (a reflection signal indicated by a symbol H1 in FIG. 4B). Equivalent to) is collected. When the reflected sound waves are collected by the microphone 2, the distance to the reflection source is calculated from the propagation time and sound velocity of the sound waves from which the reflected sound waves are obtained. However, when multiple reflection occurs between the speaker 1 and the other end in the conduit S, for example, the number of times of sequential reflection in the order indicated by “reflection (number)” in FIG. 4 (3 in FIG. 4). A reflection signal (a signal indicated by a symbol H3 in FIG. 4B) regarding the reflected sound wave is obtained at a timing shifted by the propagation time of the sound wave according to the number of times of reflection. Therefore, there is a possibility that the reflection source may be erroneously determined to be present at the position corresponding to the reception timing of the reflection signal (the signal indicated by the symbol H3).

The object of the present invention is to prevent the multiple reflections occurring in the tube and to receive only the reflected sound waves from the existing reflection source in the tube, in view of the problem in the case of using the above-mentioned conventional acoustic wave type channel survey system. An object of the present invention is to provide a multiple reflection preventing method that can be performed.

[0006]

In order to achieve this object, the invention according to claim 1 provides a sounding means for transmitting a pulsed sound wave from one end of the conduit to the inside of the conduit, and at one end of the conduit. A sound wave for investigating the inside of the pipeline from the time from the transmission of the pulsed sound wave to the collection of the sound wave using the sound collecting means for collecting the pulsed sound wave reflected in the pipeline and the sound velocity value. In the type pipe survey system, the sound collecting means is arranged at a position before reflected sound waves reach the sound generating means,
It is characterized in that one end of the conduit is switched to a non-reflection state immediately after the sound wave is transmitted by the sounding means.

According to a second aspect of the present invention, in the method of preventing multiple reflection in a pipe in the acoustic wave channel survey system according to the first aspect, the control section immediately after the reflected sound waves are collected by the sound collecting means, It is characterized in that the sounding means is driven so as to have a phase opposite to that of the reflected sound wave so that the sound is not reflected.

According to a third aspect of the present invention, in the method for preventing multiple reflection in a pipe in the acoustic wave type channel survey system according to the first aspect, the sounding means is connected to the output side, and the sound collecting means is connected to the input side. And a non-reflective state by outputting a voltage so that a sound wave having a phase opposite to that of the sound wave collected by the sound collecting means is sent from the sounding means. .

According to a fourth aspect of the invention, in the method for preventing multiple reflection in a pipe in the sound wave type channel survey system according to the first aspect, the sounding means is connected to the output side, and the sound collecting means is connected to the input side. It is characterized in that the control section controls the sounding means so that no output is generated from the sound collecting means.

The invention according to claim 5 is the invention according to claim 3 or 4.
In the method for preventing multiple reflection in a pipe in the sonic type pipe survey system described above, the control unit stores a voltage waveform output to the sounding unit, compares the voltage waveform with the output waveform from the sound collecting unit, and collects the sound collecting unit. It is characterized in that the voltage waveform output to the sounding means is changed so that no output is generated from the above.

According to a sixth aspect of the invention, in the method for preventing multiple reflection in a pipe in the acoustic wave type channel survey system according to the fifth aspect, the voltage waveform output to the sounding means is changed a plurality of times. .

According to a seventh aspect of the present invention, in the method for preventing multiple reflection in a pipe in the acoustic wave type channel survey system according to the sixth aspect, the sound collecting means changes the voltage waveform output to the sound producing means by the reflected sound waves. The feature is that the sound is collected in order.

According to an eighth aspect of the present invention, in the method for preventing multiple reflection in a pipe in the sound wave type pipe survey system according to the first aspect, the sounding means and the sound absorbing member are individually arranged at one end of the pipe line, and a sound wave is generated. Immediately after the delivery, the communication state with one end of the pipeline is switched to the communication state with the sound absorbing member.

[0014]

According to the present invention, the sound generating means is switched to the non-reflecting state immediately after the sound waves are collected by the sound collecting means, so that the reflection in the sound generating means is suppressed and the multiple reflected sound waves are not generated. Can be

According to the third aspect of the invention, the sounding means sends out a sound wave having a phase opposite to that of the sound wave collected by the control unit connected to the output side, thereby canceling the sound wave sent before. You can

According to the fourth aspect of the invention,
After the reflected sound waves are collected, the sounding means is controlled so that the output from the sound collecting means is not generated.

According to the fifth aspect of the invention, after the sound waves transmitted from the sounding means and used for the pipe line investigation are collected,
The voltage waveform applied to the sounding means is controlled so that multiple reflection sound waves are not generated, the waveform of the collected sound waves is compared with the applied voltage waveform, and the voltage waveform is changed so that multiple reflections do not occur. To do.

In the invention described in claim 6, the change of the voltage waveform in the invention described in claim 5 is repeated until the reflected sound wave can be completely canceled.

According to the invention of claim 7, when the voltage waveform is changed, the voltage waveform is sequentially changed in the transmission order of the transmitted sound waves in order to cancel the reflected sound waves. It is possible to prevent a large number of sound waves for canceling from being mixed when they are not cancelled.

According to the invention described in claim 8, the end portion of the conduit is switched between the state of communication with the sound wave source and the state of communication with the sound absorbing member, so that the sound wave is transmitted and the sound wave is absorbed after the sound wave is transmitted. Therefore, multiple reflection can be prevented.

[0021]

The present invention will be described in detail below. FIG. 1 is a block diagram showing the configuration of an apparatus used in the multiple reflection preventing method according to the first, second and third aspects of the present invention. Among the reference numerals used in FIG. 1, the same members as those shown in FIG. 4 are indicated by the same reference numerals. In FIG. 1 (A), the multiple reflection preventing apparatus 10 has a speaker 1 and a microphone 2 arranged at one of the ends of a conduit S, and the speaker 1 and the microphone 2 are electrically connected to a control unit 3 described later. Connected to each other. Microphone 2
It is arranged in front of the speaker 1. Microphone 2
The position of is a position where the reflected sound wave that is sent from the speaker 1 and reflected at an end other than one end of the conduit S can be collected by the microphone 2 before being reflected by the speaker 1. The distance (the distance indicated by the symbol L in FIG. 1A) is known. The control unit 3 is composed of a microcomputer for generating pulsed sound waves used for in-pipe inspection and for calculating the distance from the reception timing of the reflected sound waves collected by the microphone 2 to the reflection source. In addition to the function of generating the sound wave and calculating the distance to the reflection source, the control unit 3 receives the sound wave at the reception timing of the sound wave that is collected from the speaker 1 and propagates toward the end other than the sound wave sending end. Except for the above, it also has a function of switching the speaker 1 to the non-reflection state based on the reception timing of the reflected sound wave received after the reception timing. In this embodiment, as a method for setting the non-reflection state, a voltage is applied to the speaker 1 so that a sound wave having the same amplitude as the sound wave collected by the microphone 2 but an opposite phase is transmitted. In the control unit 3 described above, in order to distinguish a sound wave collected by the microphone 2 from a reflected sound wave while being transmitted from the speaker 1 and propagating to an end other than one end of the conduit S, the speaker 1 The distance between the microphone 2 and the microphone 2 is compared with the reception timing of the sound wave. That is, since the distance (L) between the speaker 1 and the microphone 2 is known, if the distance calculated from the reception timing of the sound wave and the sound velocity described above matches this distance, the sound wave is reflected. It can be distinguished that it is not a sound wave.

In this embodiment, when a pulsed sound wave is transmitted from the speaker 1 for conducting an in-pipe inspection using the multiple reflection preventing apparatus 10 as described above, "reflection (1)" is shown in FIG. 1 (B). As shown in the figure, the reflected sound wave reflected at the end other than one end of the conduit S is collected by the microphone 2 at the reception timing shown in FIG. 1 (C).
Note that in FIG. 1C, the waveform of the sound wave collected by the microphone 2 while being transmitted from the speaker 1 and propagating toward one end of the conduit S other than one end is for convenience of description. , Not displayed. When the control unit 3 determines the timing at which the reflected sound wave from an end other than one of the ends of the conduit S is received, the control unit 3 switches the speaker 1 to the non-reflection state. As a result, sound waves that are supposed to be reflected by the speaker 1 (sound waves labeled as "reflection (2)" and "reflection (3)" in FIG. 1 (B)) when the non-reflection state cannot be switched are not generated. , Figure 1
The received data regarding the multiple reflected sound waves indicated by the broken line in (C) cannot be obtained. Therefore, in the received data, the pipeline S
Only the reception timing for reflected sound waves from one end other than one of the ends is revealed.

Next, the invention according to claim 4 will be described. The invention according to claim 4 is characterized in that the sounding means is controlled so that the sound wave is not generated from the sounding means after the sound wave sent out for the duct investigation is collected by the sound collecting means. That is, in FIG. 1 (C), after the reflected sound wave (the sound wave indicated as reflection (1)) from the end other than one end of the conduit S is collected, FIG. When observing the presence or absence of a sound wave at the reception timing corresponding to the known distance (L) indicated by the reference symbol L in FIG. 1, multiple reflection (reflection indicated as reflection (2) in FIG. 1B) is generated by the speaker 1. In this case, the multiple reflected sound waves are collected by the microphone 2. For this reason,
On the received data shown in (C), the reflected sound wave labeled as "Reflection (2)" in FIG. 1B (see FIG. 1C).
Inside, the sound wave labeled as reflection (2) will be received. In the present embodiment, a received signal corresponding to the output from the microphone 2 at the time of collecting the reflected sound wave as described above (the signal labeled as reflection (2) in FIG. 1C).
The speaker 1 is switched to the non-reflection state by controlling the voltage output to the speaker 1 so as not to output.

Next, the inventions described in claims 5, 6 and 7 will be described. The invention described in each of the above claims is to control the voltage applied to the sounding means so that the multiple reflected sound waves are not generated after the sound waves sent for the purpose of pipe investigation are collected, and the waveform of the voltage is controlled. It is characterized in that a non-reflection state of the speaker 1 is obtained by changing it. FIG. 2 is a timing chart for explaining the above-mentioned features, where the left side shows the output data from the microphone 2 and the right side shows the output data of the voltage output to the speaker 1. The structure for obtaining each data shown in FIG. 2 is the same as the structure shown in FIG. In FIG. 2, a sound wave having a phase opposite to that of the collected sound wave is sent immediately after the reception signal relating to the reflected sound wave obtained by reflecting the sent sound wave used for the duct investigation is obtained. Speaker 1
Although a voltage is applied to, the sound wave of opposite phase should have a waveform corresponding to the output waveform of the voltage, but it may not correspond to the voltage waveform due to the frequency characteristic of the speaker 1 itself. Therefore, even if a voltage is output to the speaker 1 to eliminate the multiple reflected sound wave generated in the speaker 1, it is not completely eliminated. As shown by the reference numeral S1 ′ on the output data from the microphone 2 in FIG. Multiple reflected sound waves may appear.

In this embodiment, the voltage waveform output to the speaker 1 is stored, and compared with the output waveform corresponding to the multiple reflected sound waves collected by the microphone 2, the microphone 2 is compared.
The voltage waveform for the speaker 1 is changed so that the output from the speaker is not generated. That is, in FIG. 2, although the speaker 1 is driven in order to cancel the multiple reflected sound wave from the speaker 1 by the voltage waveform output at the timing indicated by reference sign S1 ′, the output from the microphone 2 regarding the multiple reflected sound wave is obtained. When the reflected sound wave is obtained, the waveform of the output voltage to the speaker 1 when the reflected sound wave is obtained is stored, and the output voltage to the speaker 1 is compared with the output waveform obtained from the microphone 2 so that the output is not generated. 2 is changed to the waveform at the timing indicated by reference sign S2 ′ on the output data of the voltage output to the speaker 1 in FIG. As a result, in the output data of the microphone 2 in FIG. 2, the output from the microphone 2 cannot be obtained at the timing indicated by the reference symbol S2 ′, so that the multiple reflected sound waves are canceled.

As a procedure for changing the waveform of the voltage output to the speaker 1 so that the output from the microphone 2 is not generated, reference symbols S1 'and S in FIG.
As shown by the timing 2 ′, if the multiple reflected sound waves are not eliminated by sending out the canceling sound waves once, the cancellation sound waves are executed multiple times.

Further, the change of the voltage is carried out sequentially in the order in which the sound is collected by the microphone 2, and like the procedure described with reference to FIG. After the sound wave is erased, a voltage for changing the voltage waveform is output again for the next-stage canceling sound wave. This prevents a large number of canceling sound waves from being mixed when the canceling sound wave of the next stage is sent out while the cancellation of the multiple reflected sound wave by the first canceling sound wave is not completed, and the voltage waveform is again detected. It is possible to prevent the task of changing the voltage waveform from becoming difficult because the canceling sound wave to be changed cannot be specified.

Next, the invention according to claim 8 will be described. In the invention according to claim 8, the sounding means and the sound absorbing member are individually provided at one end of the pipe line, and the communication state with the pipe line is switched, and when the communication state with the sound absorbing member is switched, one end of the pipe line is formed. It is characterized by the fact that no reflection occurs. Figure 3
FIG. 3 is a schematic diagram showing a configuration for obtaining the above characteristics. In FIG. 1, one end of the conduit S is formed in a bifurcated shape, and the speaker 1 and the sound absorbing member 20 are arranged at each end. . A switching member 21 such as a shutter is swingably supported at a bifurcated branching portion so that any one of the end portions can be closed. Although not shown, the microphone that is the sound collecting unit is arranged in front of the sound absorbing member 20.

In the present embodiment, the switching member 21 is operated to the position where the speaker 1 communicates with the conduit S during sound wave transmission. When the sound wave transmission from the speaker 1 is completed, the switching member 21 is operated so that the sound absorbing member 20 and the conduit S are brought into communication with each other. As a result, after the reflected sound wave from the end portion other than one end of the pipe is collected by the microphone (not shown) and reaches the sound absorbing member 20, it is not absorbed and reflected.

[0030]

According to the inventions of claims 1 and 2,
Immediately after the sound waves are collected by the sound collecting means, the sound generating means is switched to the non-reflective state, whereby the reflection at the sound generating means is suppressed and the multiple reflected sound waves can be prevented from being generated.

According to the third aspect of the present invention, the sounding means is driven so that the sounding means sends out a sound wave having a phase opposite to that of the sound wave collected by the control section connected to the output side. Generation of reflected sound waves can be prevented.

According to the fourth aspect of the invention, the sounding means is arranged so that the control section does not generate an output from the sound collecting means after the sound waves sent from the sounding means for the purpose of pipe line investigation are collected. Is controlled, so that multiple reflection at the sounding means is prevented.

According to the present invention, the voltage waveform used for transmitting the sound wave for preventing the generation of the multiple reflected sound wave after collecting the sound wave sent from the sounding means and used for the duct investigation is used. As a control target, the waveform of the collected sound wave is compared with the voltage waveform applied to the sounding means, and the voltage waveform is changed so that the output from the sound collecting means is not generated. The sound wave used is prevented from being multiply reflected by the sounding means.

According to the sixth aspect of the invention, in addition to the effect of the fifth aspect of the invention, the change of the voltage waveform can be repeated until the reflected sound waves can be canceled completely, and the generation of the reflected sound waves can be eliminated. it can.

According to the invention of claim 7, when the voltage waveform is changed, the sound collecting means sequentially changes the voltage waveform in the order in which the reflected sound waves are collected, so that the reflected sound waves are temporarily changed by changing the voltage waveform at the first stage. It is possible to prevent a large number of sound waves for canceling from being mixed when the canceling noise is not cancelled.

According to the invention described in claim 8, by switching the end portion of the conduit to the state of communication with the sound wave source and the state of communication with the sound absorbing member, the sound wave is transmitted and the sound wave is absorbed after the sound wave is transmitted. It is possible to prevent multiple reflections.

[Brief description of drawings]

FIG. 1 is a block diagram for explaining an embodiment of a multiple reflection preventing method according to the first to fourth aspects of the present invention and a timing chart showing a reception timing regarding reflected sound waves for explaining the operation in the configuration.

FIG. 2 is a timing chart showing voltage waveform data and sound wave reception data for explaining an embodiment of the multiple reflection preventing method according to the fifth, sixth, and seventh inventions.

FIG. 3 is a schematic diagram showing a configuration for explaining an embodiment of a multiple reflection preventing method according to the invention of claim 8;

FIG. 4 is a schematic diagram showing a format of a pipeline and a timing chart showing a reception timing of a sound wave in the pipeline for explaining a case where multiple reflection occurs in the pipeline.

[Explanation of symbols]

Speaker that is 1 sounding means 2 Microphone that is a sound collecting means 3 control unit P1, S pipeline 20 Sound absorbing member 21 Switching member

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Claims (8)

(57) [Claims] 1. A sounding means for sending a pulsed sound wave into the conduit from one end of the conduit, and a sound collecting means for collecting the pulsed sound wave reflected in the conduit at one end of the conduit. In a sound wave type pipe survey system for investigating the inside of a pipe from the time from the time when the pulsed sound wave is transmitted to the time when the sound is collected and the sound velocity value, in the sound collecting means, the sound wave is reflected by the sound generating means. An intra-pipe multiple reflection preventing method in a sonic type pipe survey system, which is arranged at a position before reaching and immediately after the sound wave is transmitted by the sounding means, one end of the pipe line is switched to a non-reflecting state. 2. The in-pipe multiple reflection preventing method in the acoustic wave channel survey system according to claim 1, wherein the control unit sets a phase opposite to the reflected sound wave immediately after the reflected sound wave is collected by the sound collecting means. A method for preventing multiple reflection in a pipe in a sound wave type pipe survey system, characterized in that the sound generating means is driven into a non-reflective state. 3. The method for preventing multiple reflection in a pipe in a sonic type pipe survey system according to claim 1, wherein the sounding means is connected to the output side, and the input side is provided with a control section to which the sound collecting means is connected. The control section outputs a voltage so that a sound wave having a phase opposite to that of the sound wave picked up by the sound collecting means is sent from the sounding means so as to be in a non-reflective state. Method for preventing multiple reflections in pipes. 4. The method for preventing multiple reflection in a pipe in the acoustic wave channel survey system according to claim 1, further comprising: a control unit to which the sounding means is connected to the output side and the sound collecting means is connected to the input side. The control section controls the sounding means so that no output is generated from the sound collecting means. 5. The method for preventing intra-tube multiple reflection in a sound wave type pipe survey system according to claim 3 or 4, wherein the control section stores a voltage waveform output to the sound producing means, and outputs the sound from the sound collecting means. An in-pipe multiple reflection preventing method in a sound wave type pipe survey system, characterized in that a voltage waveform outputted to said sound producing means is changed so as not to generate an output from said sound collecting means as compared with the output waveform. 6. The acoustic wave channel survey system according to claim 5, wherein the voltage waveform output to the sound producing means is changed a plurality of times in the method for preventing multiple reflection in a tube in the acoustic wave channel survey system. Method for preventing multiple reflections in pipes. 7. The in-pipe multiple reflection preventing method in the acoustic wave channel survey system according to claim 6, wherein the voltage waveform output to the sound producing means is changed in order in which the sound collecting means collects the reflected sound waves. A method for preventing multiple reflection inside a pipe in a sonic pipe survey system characterized by performing. 8. The method for preventing multiple reflection in a pipe in a sonic type pipe survey system according to claim 1, wherein the sounding means and the sound absorbing member are individually arranged at one end of the pipe line, and the pipe line is immediately after the sound wave is transmitted. A method for preventing multiple reflection in a pipe in a sound wave type pipe survey system, characterized by switching from a communication state with one end of the sound absorbing member to a communication state with the sound absorbing member.