Liquid detection system and liquid detection method

Abstract

Provided is a liquid detection system with which it is possible to accurately determine whether a liquid is present in a metal pipe. A liquid detection system (1) comprises a first ultrasonic transducer (3), a drive circuit (4), a second ultrasonic transducer (5), a detection circuit (6), and an output unit (7a). The first ultrasonic transducer (3) is attached to metal piping (21) that is subject to measurement. The drive circuit (4) causes ultrasonic waves to be oscillated from the first ultrasonic transducer (3). The second ultrasonic transducer (5) is attached to the piping (21) on the side opposite from the first ultrasonic transducer (3) and receives TTE waves of the ultrasonic waves oscillated from the first ultrasonic transducer (3). The detection circuit (6) detects the reception waveform of the TTE waves received by the second ultrasonic transducer (5). The output unit (7a) outputs waveform information relating to the reception waveform of the TTE waves detected by the detection circuit (6).

Description

Liquid detection system and liquid detection method

[0001] The present invention relates generally to a liquid detection system and a liquid detection method, and more particularly to a liquid detection system and a liquid detection method used to determine the presence or absence of liquid in a pipe.

[0002] The ultrasonic air bubble detector (liquid detection system) described in Patent Document 1 includes a pair of ultrasonic transducers facing each other across a liquid transport pipe (piping) through which the liquid flows. In this ultrasonic air bubble detector, ultrasonic waves emitted from one of the ultrasonic transducers pass through the liquid transport pipe and the liquid and are received by the other ultrasonic transducer. When bubbles are present in the liquid, the ultrasonic waves are scattered and absorbed by the bubbles, reducing the intensity of the received ultrasonic waves. This phenomenon is utilized to detect the presence or absence of liquid in the liquid transport pipe.

[0003] Japanese Patent Application Publication No. 11-319081

[0004] In the ultrasonic bubble detector described in Patent Document 1, the liquid transport pipe is made of a soft, easily deformable material such as polymer resin or rubber. Because such materials have difficulty transmitting ultrasonic waves, ultrasonic waves propagating through the liquid transport pipe do not become noise. However, if the liquid transport pipe is made of metal, ultrasonic waves propagating through the metal part of the liquid transport pipe interfere with ultrasonic waves propagating through the liquid in the liquid transport pipe, resulting in noise. Therefore, if the liquid transport pipe is made of metal, it is difficult to accurately detect the presence or absence of liquid in the liquid transport pipe.

[0005] In view of the above problems, an object of the present invention is to provide a liquid detection system and a liquid detection method that can accurately determine the presence or absence of liquid in a metal pipe.

[0006] A liquid detection system according to one aspect of the present invention includes a first ultrasonic transducer, a drive circuit, a second ultrasonic transducer, a detection circuit, and an output unit. The first ultrasonic transducer is attached to a metal pipe to be measured. The drive circuit causes the first ultrasonic transducer to emit ultrasonic waves. The second ultrasonic transducer is attached to the pipe on the opposite side from the first ultrasonic transducer and receives the ultrasonic TTE waves emitted from the first ultrasonic transducer. The detection circuit detects the received waveform of the TTE waves received by the second ultrasonic transducer. The output unit outputs waveform information related to the received waveform of the TTE waves detected by the detection circuit.

[0007] A liquid detection system according to one aspect of the present invention includes a first ultrasonic transducer, a drive circuit, a second ultrasonic transducer, a detection circuit, and an output unit. The first ultrasonic transducer is attached to a metal pipe to be measured. The drive circuit causes the first ultrasonic transducer to emit ultrasonic waves. The second ultrasonic transducer is attached to the pipe around the first ultrasonic transducer and receives the ultrasonic QTE waves emitted from the first ultrasonic transducer. The detection circuit detects the received waveform of the ultrasonic QTE waves received by the second ultrasonic transducer. The output unit outputs waveform information related to the received waveform of the QTE waves detected by the detection circuit.

[0008] A liquid detection system according to one aspect of the present invention includes an ultrasonic transducer, a drive circuit, a detection circuit, a switching circuit, and an output unit. The ultrasonic transducer is attached to a metal pipe to be measured. The drive circuit is connected to the ultrasonic transducer and causes the ultrasonic transducer to emit ultrasonic waves. The detection circuit is connected to the ultrasonic transducer and detects the received waveform of the QTE wave of the ultrasonic wave received by the ultrasonic transducer. After connecting the ultrasonic transducer to the drive circuit, the switching circuit separates the ultrasonic transducer from the drive circuit and connects it to the detection circuit. The output unit outputs waveform information regarding the received waveform of the QTE wave detected by the detection circuit.

[0009] A liquid detection method according to one aspect of the present invention includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a first ultrasonic transducer is attached to a metal pipe to be measured. In the second step, ultrasonic waves are emitted from the first ultrasonic transducer by a drive circuit. In the third step, a second ultrasonic transducer is attached to the pipe on the opposite side from the first ultrasonic transducer, and the second ultrasonic transducer receives the ultrasonic TTE waves emitted from the first ultrasonic transducer. In the fourth step, the received waveform of the ultrasonic TTE waves received by the second ultrasonic transducer is detected by a detection circuit. In the fifth step, waveform information regarding the received waveform of the TTE waves detected by the detection circuit is output from an output unit.

[0010] A liquid detection method according to one aspect of the present invention includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a first ultrasonic transducer is attached to a metal pipe to be measured. In the second step, ultrasonic waves are emitted from the first ultrasonic transducer by a drive circuit. In the third step, a second ultrasonic transducer is attached to the pipe around the first ultrasonic transducer, and the second ultrasonic transducer receives the ultrasonic QTE waves emitted from the first ultrasonic transducer. In the fourth step, a detection circuit detects the received waveform of the QTE waves received by the second ultrasonic transducer. In the fifth step, waveform information regarding the received waveform of the QTE waves detected by the detection circuit is output from an output unit.

[0011] A liquid detection method according to one aspect of the present invention includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, an ultrasonic transducer is attached to a metal pipe to be measured. In the second step, an ultrasonic transducer is caused to emit ultrasonic waves by a drive circuit. In the third step, a received waveform of the ultrasonic waves received by the ultrasonic transducer is detected by a detection circuit. In the fourth step, the ultrasonic transducer is connected to the drive circuit, and then the ultrasonic transducer is separated from the drive circuit and connected to the detection circuit. In the fifth step, waveform information regarding the received waveform of the QTE wave detected by the detection circuit is output from an output unit.

[0012] The liquid detection system and liquid detection method according to one aspect of the present invention have the advantage of being able to accurately determine whether or not a liquid is present in a metal pipe.

[0013] FIG. 1 is a diagram illustrating the configuration of a liquid detection system according to a first embodiment. FIG. 2 is an explanatory diagram illustrating ultrasonic waves propagating through a pipe in the liquid detection system. FIG. 3 is a graph illustrating a waveform received by a second ultrasonic transducer in the liquid detection system when there is no liquid in the pipe. FIG. 4 is a graph illustrating a waveform received by a second ultrasonic transducer in the liquid detection system when there is liquid in the pipe. FIG. 5 is an explanatory diagram illustrating the definition of a pipe wall propagating wave. FIG. 6 is an explanatory diagram illustrating the definition of a submerged propagating wave. FIG. 7 is an explanatory diagram illustrating another definition of a pipe wall propagating wave. FIG. 8 is an explanatory diagram illustrating a liquid detection system according to a second modification of the first embodiment. FIG. 9 is an explanatory diagram illustrating a liquid detection system according to a third modification of the first embodiment. FIG. 10 is an explanatory diagram illustrating a liquid detection system according to a fourth modification of the first embodiment. FIG. 11 is an explanatory diagram illustrating a liquid detection system according to a fifth modification of the first embodiment. FIG. 12 is a diagram illustrating the configuration of a liquid detection system according to the second embodiment. Fig. 13 is a graph showing a waveform received by an ultrasonic vibrator in the above liquid detection system when there is no liquid in the pipe. Fig. 14 is a graph showing a waveform received by an ultrasonic vibrator in the above liquid detection system when there is liquid in the pipe. Fig. 15 is a configuration diagram showing the configuration of a liquid detection system according to embodiment 3. Fig. 16 is a configuration diagram showing the configuration of a liquid detection system according to embodiment 4. Fig. 17 is a configuration diagram showing the configuration of a liquid detection system according to embodiment 5.

[0014] First Embodiment A liquid detection system 1 according to a first embodiment will be described in detail with reference to the drawings.

[0015] (1) Overview As shown in FIG. 1 , a liquid detection system 1 according to the first embodiment includes a first ultrasonic transducer 3, a drive circuit 4, a second ultrasonic transducer 5, a detection circuit 6, and an output unit 7a. The first ultrasonic transducer 3 is attached to a metal pipe 21 that is the measurement target. The drive circuit 4 causes the first ultrasonic transducer 3 to emit ultrasonic waves. The second ultrasonic transducer 5 is attached to the pipe 21 on the opposite side from the first ultrasonic transducer 3, and receives triple transit echo (TTE) waves of the ultrasonic waves emitted from the first ultrasonic transducer 3. The detection circuit 6 detects the received waveform of the TTE waves received by the second ultrasonic transducer 5. The output unit 7a outputs waveform information related to the received waveform of the TTE waves detected by the detection circuit 6.

[0016] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be determined with high accuracy based on the received waveform of the TTE wave.

[0017] (2) Details of Configuration As shown in FIG. 1 , the liquid detection system 1 according to the first embodiment is used to determine the presence or absence of a liquid in a metal pipe 21. The pipe 21 is made of metal and has, for example, a cylindrical shape. The pipe 21 is used, for example, as a raw material supply pipe in a factory. That is, the liquid detection system 1 can be used to determine the presence or absence of a liquid in the metal pipe 21, for example, a raw material supply pipe in a factory. Note that the use of the liquid detection system 1 is not limited to raw material supply pipes in a factory, and the liquid detection system 1 can be applied to any metal pipe for any purpose as long as it is used to determine the presence or absence of a liquid in the metal pipe.

[0018] As shown in FIG. 1, the liquid detection system 1 includes a first ultrasonic transducer 3, a drive circuit 4, a second ultrasonic transducer 5, a detection circuit 6, and a processor 7.

[0019] The first ultrasonic vibrator 3 is attached to the metal pipe 21 to be measured. The first ultrasonic vibrator 3 is an ultrasonic vibrator for oscillating ultrasonic waves. The first ultrasonic vibrator 3 oscillates ultrasonic waves at a second frequency in response to a drive signal at a first frequency from the drive circuit 4. More specifically, when the drive signal at the first frequency is input from the drive circuit 4, the first ultrasonic vibrator 3 vibrates at a second frequency corresponding to the first frequency of the input drive signal, thereby oscillating ultrasonic waves at the second frequency corresponding to the first frequency of the input drive signal. The first ultrasonic vibrator 3 includes, for example, a piezoelectric element. The piezoelectric element is an element that converts electrical vibrations into mechanical vibrations. In the first embodiment, the piezoelectric element converts the drive signal (electrical vibrations) from the drive circuit into mechanical vibrations and oscillates the converted mechanical vibrations as ultrasonic waves. The first ultrasonic vibrator 3 oscillates, for example, pulse waves with a center frequency of 1 to 10 MHz as ultrasonic waves.

[0020] The first ultrasonic vibrator 3 has, for example, a rectangular parallelepiped outer shape. The first ultrasonic vibrator 3 has a contact surface 3a that comes into contact with a predetermined area of ​​the outer surface 21a of the pipe 21. The contact surface 3a has a concave curved portion with the same curved shape as the shape (convex curved portion) of the predetermined area of ​​the outer surface 21a of the pipe 21. The first ultrasonic vibrator 3 is attached to the predetermined area of ​​the outer surface 21a by bringing the contact surface 3a into surface contact with the predetermined area of ​​the outer surface 21a of the pipe 21. The first ultrasonic vibrator 3 is fixed to the outer surface 21a of the pipe 21 by, for example, an adhesive.

[0021] The drive circuit 4 is electrically connected to the first ultrasonic transducer 3. The drive circuit 4 inputs a drive signal of a first frequency to the first ultrasonic transducer 3, causing the first ultrasonic transducer 3 to oscillate ultrasonic waves of a second frequency corresponding to the first frequency of the drive signal.

[0022] The second ultrasonic transducer 5 is attached to the outer surface 21a of the metal pipe 21, which is the measurement target, on the opposite side to the first ultrasonic transducer 3. That is, the first ultrasonic transducer 3 and the second ultrasonic transducer 5 are attached to the outer surface 21a of the pipe 21 so as to face each other across the pipe 21. The second ultrasonic transducer 5 is a receiving ultrasonic transducer that receives ultrasonic waves. The second ultrasonic transducer 5 receives ultrasonic waves (e.g., fundamental waves and TTE waves) emitted from the first ultrasonic transducer 3. When the second ultrasonic transducer 5 receives ultrasonic waves from the first ultrasonic transducer 3, it generates an electrical signal corresponding to the waveform of the received ultrasonic waves and outputs the generated electrical signal as a received wave to the detection circuit 6. The second ultrasonic transducer 5 has, for example, a piezoelectric element. The piezoelectric element converts the mechanical vibration of the ultrasonic waves (received waves) received by the second ultrasonic transducer 5 into an electrical AC signal and outputs the electrical AC signal as the received wave.

[0023] The second ultrasonic vibrator 5 has, for example, the same external shape (e.g., a rectangular parallelepiped shape) as the first ultrasonic vibrator 3. The second ultrasonic vibrator 5 has a contact surface 5a that comes into contact with a predetermined area of ​​the outer surface 21a of the pipe 21. The contact surface 5a has a concave curved surface portion with the same curved shape as the shape (convex curved surface portion) of the predetermined area of ​​the outer surface 21a of the pipe 21. The second ultrasonic vibrator 5 is attached to the predetermined area of ​​the outer surface 21a of the pipe 21 by bringing the contact surface 5a into surface contact with the predetermined area of ​​the outer surface 21a of the pipe 21. The second ultrasonic vibrator 5 is fixed to the outer surface 21a of the pipe 21 by, for example, an adhesive.

[0024] The detection circuit 6 is electrically connected to the second ultrasonic transducer 5. The detection circuit 6 detects the received waveform of the ultrasonic waves (e.g., fundamental wave and TTE wave) received by the second ultrasonic transducer 5 based on the received waves from the second ultrasonic transducer 5. Here, the "received waveform" refers to the change over time in the amplitude (voltage) of the ultrasonic waves received by the second ultrasonic transducer 5. The detection circuit 6 then outputs the detected received waveform to the processor 7 as the detection result.

[0025] The processor 7 functions as a signal generator and a measuring device. The processor 7 is electrically connected to the drive circuit 4 and the detection circuit 6. The processor 7 functions as a signal generator when causing the first ultrasonic transducer 3 to oscillate ultrasonic waves. When the processor 7 functions as a signal generator, it outputs a control signal to the drive circuit 4 for causing the first ultrasonic transducer 3 to oscillate ultrasonic waves. When the control signal is input from the processor 7, the drive circuit 4 inputs a drive signal of the first frequency to the first ultrasonic transducer 3, as described above, thereby causing the first ultrasonic transducer 3 to oscillate ultrasonic waves of the second frequency.

[0026] The processor 7 has an output unit 7a. The output unit 7a is a display unit (e.g., a monitor) capable of displaying the detection results of the detection circuit 6, for example, as a graph. In this graph, the vertical axis represents amplitude (voltage) and the horizontal axis represents time. When the detection results are input from the detection circuit 6, the processor 7 functions as a measuring device. When functioning as a measuring device, the processor 7 outputs the detection results input from the detection circuit 6 to the output unit 7a, for example, as a graph. This output allows the detection results of the detection circuit 6 to be presented to the user in a visually easy-to-understand manner. In the first embodiment, the output unit 7a is a display unit that displays the detection results of the detection circuit 6. However, the output unit 7a may be configured to digitally process the detection results of the detection circuit 6 (e.g., frequency range and amplitude (voltage)) within the processor 7 and output a final indication of the presence or absence of liquid (0 or 1). Furthermore, the processor 7 configured in this manner may be integrated with the drive circuit 4, the detection circuit 6, the first ultrasonic transducer 3, and the second ultrasonic transducer 5 into a modular structure.

[0027] (3) How Ultrasonic Waves Propagate in a Pipe The propagation of ultrasonic waves in the pipe 21 to be measured will be described with reference to FIG.

[0028] As shown in FIG. 2, in the liquid detection system 1, as described above, the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 are arranged on the outer surface 21a of the pipe 21 so as to face each other with the pipe 21 in between.

[0029] 2 is the propagation path of a propagation wave (pipe wall propagation wave C1a) that propagates through the pipe wall (metal part 21b) of pipe 21. Propagation path C2 in FIG. 2 is the propagation path of a propagation wave (a direct submerged propagation wave (also called a direct submerged propagation wave) C2a) that propagates directly through the liquid inside pipe 21 (hollow part 21c). Propagation path C3 in FIG. 2 is the propagation path of a TTE wave C3a. Symbol R [mm] in FIG. 2 indicates the outer diameter of pipe 21, symbol r [mm] in FIG. 2 indicates the inner diameter of pipe 21, and symbol d [mm] in FIG. 2 indicates the thickness of the pipe wall (metal part 21b) of pipe 21. In the following description, the sound speed of the propagating wave propagating through the pipe wall of the pipe 21 (piping material sound speed) may be referred to as Vp [m / s], and the sound speed of the propagating wave propagating through the liquid inside the pipe 21 (liquid sound speed) may be referred to as Vl [m / s]. In Fig. 2, the propagating wave (pipe wall propagating wave C1a) is depicted as propagating inside the pipe 21 for convenience of illustration, but in reality it is the pipe wall and therefore propagates on the outer surface of the pipe 21.

[0030] When there is no liquid in the hollow portion 21c of the pipe 21, most of the ultrasonic waves emitted from the first ultrasonic transducer 3 propagate as pipe wall propagating waves C1a around half a circumference of the metal portion 21b of the pipe 21, as shown in propagation path C1, and are received by the second ultrasonic transducer 5. In this case, the ultrasonic waves emitted from the first ultrasonic transducer 3 hardly propagate through the air in the hollow portion 21c of the pipe 21. For this reason, as shown in Figure 3, the waveform received by the second ultrasonic transducer 5 when there is no liquid in the hollow portion 21c of the pipe 21 (the detection result of the detection circuit 6, i.e., the received waveform of the pipe wall propagating waves C1a) appears as waveform C1a in Figure 3. In the graph of Figure 3, the horizontal axis is time (μs) and the vertical axis is voltage (mV), with time being set to 0 when the ultrasonic waves are emitted from the first ultrasonic transducer 3, and the voltage represents the signal level received by the second ultrasonic transducer 5. In the example of Fig. 3, the pipe wall propagation wave C1a appears in a section of approximately 5 µs to 20 µs. tps (time pipe start) in Fig. 3 is the arrival time of the pipe wall propagation wave C1a.

[0031] When there is liquid in the hollow portion 21c of the pipe 21, the ultrasonic waves emitted from the first ultrasonic transducer 3 propagate as pipe wall propagating waves C1a around half a circumference of the metal portion 21b of the pipe 21, as shown in propagation path C1, and are received by the second ultrasonic transducer 5. In this case, the ultrasonic waves emitted from the first ultrasonic transducer 3 further propagate through the liquid in the hollow portion 21c of the pipe 21 as direct submerged propagating waves C2a (propagation path C2) and TTE waves C3a (propagation path C3), and are received by the second ultrasonic transducer 5. More specifically, the direct submerged propagating waves C2a propagate through the liquid in the hollow portion 21c of the pipe 21 from the first ultrasonic transducer 3 to the second ultrasonic transducer 5, and are directly received by the second ultrasonic transducer 5. The TTE wave C3a propagates through the liquid in the cavity 21c of the pipe 21 in the radial direction of the pipe 21 by being reflected once by the inner surface of the pipe 21, making one and a half round trips, and is then received by the second ultrasonic transducer 5. That is, the TTE wave C3a propagates through the liquid in the cavity 21c of the pipe 21 one extra round trip compared to the sub-liquid direct propagation wave C2a, and therefore the TTE wave C3a is received by the second ultrasonic transducer 5 with a sufficient delay from the pipe wall propagation wave C1a and the sub-liquid direct propagation wave C2a (i.e., such that the waveforms of the two waves are separated in time).

[0032] 4, when liquid is present in the cavity 21c of the pipe 21, the received waveform of the second ultrasonic transducer 5 (detection result of the detection circuit 6) includes a waveform of the pipe wall propagating wave C1a, a waveform of the submerged direct propagating wave C2a, and a waveform of the TTE wave C3a. The TTE wave C3a propagates one extra round trip through the cavity 21c of the pipe 21 compared to the pipe wall propagating wave C1a and the submerged direct propagating wave C2a, and therefore appears with a certain time delay after the waveforms of the pipe wall propagating wave C1a and the submerged direct propagating wave C2a appear. In the example of FIG. 4, the pipe wall propagating wave C1a and the submerged direct propagating wave C2a appear in a range of approximately 5 μs to 20 μs, and the TTE wave C3a appears in a range of approximately 25 μs to 35 μs. 3, tls1 is the arrival time of the direct wave of the submerged propagation wave (submerged direct propagation wave) C2a, and tls3 is the arrival time of the TTE wave C3a.

[0033] 3 and 4, the received waveforms (reception time range and reception intensity) of the pipe wall propagating wave C1a and the submerged direct propagating wave C2a when there is liquid in the cavity 21c of the pipe 21 (FIG. 4) are difficult to distinguish from the received waveform of the pipe wall propagating wave C1a when there is no liquid in the cavity 21c of the pipe 21 (FIG. 3). For this reason, it is difficult to determine the presence or absence of liquid in the pipe 21 based on the received waveforms of the pipe wall propagating wave C1a and the submerged direct propagating wave C2a among the waves received by the second ultrasonic transducer 5.

[0034] 3 and 4, when there is no liquid in the cavity 21c of the pipe 21 (FIG. 3), the received waveform of the TTE wave C3a does not appear, but when there is liquid in the cavity 21c of the pipe 21 (FIG. 4), the received waveform of the TTE wave C3a appears with a sufficient delay from the pipe wall propagating wave C1a and the submerged direct propagating wave C2a. Therefore, it is possible to determine the presence or absence of liquid in the pipe 21 based on the received waveform of the TTE wave C3a among the received waves of the second ultrasonic transducer 5.

[0035] (4) Conditions for the Inner Diameter of the Pipe As described above, in order to be able to determine the presence or absence of liquid in the pipe 21 based on the received waveform of the TTE wave C3a, the received waveform of the TTE wave C3a needs to be sufficiently separated in time from the received waveforms of the pipe wall propagating wave C1a and the sub-liquid direct propagating wave C2a. If the inner diameter of the pipe 21 is too small, the time difference between the received waveforms of the pipe wall propagating wave C1a and the sub-liquid direct propagating wave C2a and the received waveform of the TTE wave C3a becomes small, and the received waveform of the TTE wave C3a cannot be sufficiently separated in time from the received waveforms of the pipe wall propagating wave C1a and the sub-liquid direct propagating wave C2a. As can be seen from Figures 3 and 4, ringing of approximately 20 μs occurs in the pipe wall propagating wave C1a and the sub-liquid direct propagating wave C2a. For this reason, the propagation time of the TTE wave C3a (the time from when it is emitted from the first ultrasonic transducer 3 to when it is received by the second ultrasonic transducer 5) needs to be equal to or longer than the ringing time (20 μs) of the pipe wall propagation wave C1a and the submerged direct propagation wave C2a. In other words, when the inner diameter of the pipe 21 is D1 and the sound speed of the ultrasonic wave propagating through the liquid in the hollow portion 21c of the pipe 21 is c1, the inner diameter D1 and the sound speed c1 need to satisfy the condition of Equation 1.

[0036] 3×D1 / c1≧20 μs Equation 1 In other words, if the inner diameter D1 of the pipe 21 satisfies the relationship of Equation 1, the TTE wave C3a can be sufficiently separated in time from the pipe wall propagation wave C1a and the submerged direct propagation wave C2a. As a result, it is possible to determine the presence or absence of liquid in the pipe 21 based on the received waveform of the TTE wave C3a.

[0037] (5) Principle of Determining the Presence or Absence of Liquid in a Pipe As described above, it is difficult to determine the presence or absence of liquid in the pipe 21 based on the received waveforms of the pipe wall propagating wave C1a and the liquid direct propagating wave C2a among the received waves of the second ultrasonic transducer 5. However, it is easy to determine the presence or absence of liquid in the pipe 21 based on the received waveform of the TTE wave C3a among the received waves of the second ultrasonic transducer 5. For this reason, in the liquid detection system 1, the user determines the presence or absence of liquid in the pipe 21 based on the received waveform of the TTE wave C3a received by the second ultrasonic transducer 5. More specifically, if the received waveform of the TTE wave C3a is included in the received waves of the second ultrasonic transducer 5, it is determined that liquid is present in the pipe 21. On the other hand, if the received waves of the second ultrasonic transducer 5 do not include the received waveform of the TTE wave C3a, it is determined that no liquid is present in the pipe 21.

[0038] (6) Example of Output of Processor 7 In the liquid detection system 1, as described above, the processor 7 outputs (e.g., displays) the detection result of the detection circuit 6 to the output unit 7a. For example, the output unit 7a outputs (displays) a graph of the received waveform of the received wave of the second ultrasonic transducer 5 as the detection result of the detection circuit 6, as shown in FIG. 3 or 4. The graph of the received waveform shows the change in the amplitude (voltage) of the received wave over time, with the vertical axis representing the amplitude (voltage) of the received wave and the horizontal axis representing time, for example. FIG. 3 shows an example in which only the pipe wall propagating wave C1a is output (displayed) as the received wave, and FIG. 4 shows an example in which the pipe wall propagating wave C1a, the liquid direct propagating wave C2a, and the TTE wave C3a are output (displayed) as the received wave.

[0039] In the liquid detection system 1, the detection results of the detection circuit 6 are output (e.g., displayed) from the output unit 7a, allowing the user to recognize (e.g., visually recognize) the detection results of the detection circuit 6. The user then determines whether or not a liquid is present in the pipe 21 to be measured based on the detection results of the detection circuit 6 output from the output unit 7a. More specifically, if the detection results of the detection circuit 6 output from the output unit 7a include the TTE wave C3a, it is determined that a liquid is present in the pipe 21 to be measured. On the other hand, if the detection results of the detection circuit 6 output from the output unit 7a do not include the TTE wave C3a, it is determined that no liquid is present in the pipe 21 to be measured.

[0040] (7) Definition of Time Various times related to the propagating wave propagating through the pipe 21 are defined.

[0041] As shown in Figure 5, various times related to the pipe wall propagating wave C1a are defined. For example, the arrival time tps of the pipe wall propagating wave C1a is defined as the time when the voltage of the pipe wall propagating wave C1a exceeds a voltage v120 that is ±120% of the average voltage va of the voltage v0 when there is no signal. Also, the convergence time tpe (time pipe end) of the pipe wall propagating wave C1a is defined as the time when the voltage of the pipe wall propagating wave C1a becomes less than a voltage v120 that is ±120% of the average voltage va of the voltage v0 when there is no signal. Also, the received wave convergence time tprin (time pipe ringing) of the pipe wall propagating wave C1a is defined by the formula tprin = tpe - tps. With the above time definitions, a certain level of disturbance noise is superimposed on the received waveform of the detection circuit 6 even when no signal is being transmitted or received. For this reason, the time when the amplitude level exceeds 120% of the time when there is no signal is defined as "the start of propagation of the propagating wave," and the time when the amplitude level becomes less than 120% of the time when there is no signal is defined as "the time when the propagating wave has finished converging." Note that the value of "120%" above is an example and may be changed depending on the environment.

[0042] Similarly, various times related to the in-liquid propagating wave are defined as shown in Figure 6. For example, the arrival time tls1 (time liquid start 1st wave) of the direct wave C2a of the in-liquid propagating wave is defined as the time when the voltage of the in-liquid propagating wave exceeds a voltage v120 that is ±120% of the average voltage va of the voltage v0 when there is no signal. Also, the convergence time tle1 (time liquid end 1st wave) of the direct wave C2a of the in-liquid propagating wave is defined as the time when the voltage of the in-liquid propagating wave falls below a voltage v120 that is ±120% of the average voltage va of the voltage v0 when there is no signal. Also, the received wave convergence time tlrin1 (time liquid ringing 1st wave) of the direct wave C2a of the in-liquid propagating wave is defined by the formula tlrin1 = tle1 - tls1.

[0043] Similarly, as shown in Figure 6, various times are defined for the TTE wave C3a of the liquid-propagating wave. For example, the arrival time tls3 (time liquid start 3rd wave) of the TTE wave C3a of the liquid-propagating wave is defined as the time when the voltage of the liquid-propagating wave exceeds a voltage v120 that is ±120% of the average voltage va of the voltage v0 when there is no signal. Also, the convergence time tle3 (time liquid end 3rd wave) of the TTE wave C3a of the liquid-propagating wave is defined as the time when the voltage of the liquid-propagating wave becomes less than a voltage v120 that is ±120% of the average voltage va of the voltage v0 when there is no signal. Also, the received wave convergence time tlrin3 (time pipe ringing 3rd wave) of the TTE wave C3a of the liquid-propagating wave is defined by the formula tlrin3 = tle3 - tls3.

[0044] Also, as shown in Figure 6, various times related to the QTE wave of the liquid-propagating wave are defined. For example, the arrival time tls4 (time liquid start 4th wave) of the QTE wave of the liquid-propagating wave is defined as the time when the voltage of the liquid-propagating wave exceeds a voltage v120 that is ±120% of the average voltage v a when there is no signal. Also, the convergence time tle4 (time liquid end 4th wave) of the QTE wave of the liquid-propagating wave is defined as the time when the voltage of the liquid-propagating wave becomes less than a voltage v120 that is ±120% of the average voltage v a when there is no signal. Also, the received wave convergence time tlrin4 (time pipe ringing 4th wave) of the QTE wave of the liquid-propagating wave is defined by the formula tlrin4 = tle4 - tls4.

[0045] (8) Definition of Time (Alternative Definition) The following alternative definition of time may be used.

[0046] By using the following alternative definition of time, the effects of the waveform offset and waveform amplitude can be reduced compared to when the above definition of time is used.

[0047] As shown in FIG. 7 , in another definition of time, the time when the first waveform M1 of the propagation waveform group intersects with the average voltage va is defined as the arrival time tps of the propagation waveform group. Furthermore, the time when the falling edge of the last waveform Mn of the propagation waveform group intersects with the average voltage va is defined as the convergence time tpe of the propagation waveform group. The first waveform M1 is the first waveform among the waveforms that exceed a voltage v120, which is an increase of ±120% of the average voltage Va of the voltage v0 when there is no signal, and the nth waveform Mn is the last waveform among the waveforms that exceed the voltage v120. In this other definition of time, the zero-crossing point of the waveform when it exceeds a voltage v120, which is an increase of 120% compared to the noise (average voltage) when there is no signal, is defined as the arrival time tps, and the zero-crossing point when it becomes less than v120 is defined as the convergence time tpe. This definition can also be applied to tls.

[0048] (9) Explanation of the key points of the present invention using the above definition of time When the direct wave C2a of the submerged wave arrives before the tube wall wave C1a converges (i.e., when the following relational expression 1 holds), it is difficult to distinguish between the tube wall wave and the submerged wave.

[0049] tps < tls1 < tpe ...Relationship 1 At this time, the arrival time tls3 of the TTE wave C3a of the liquid propagating wave and the convergence time tpe of the pipe wall propagating wave C1a satisfy the following relationship 2, so that the pipe wall propagating wave C1a and the TTE wave C3a of the liquid propagating wave can be distinguished.

[0050] tpe < tls3 ... Relational Expression 2 The key point of the present invention is to use Relational Expression 2 to determine the presence or absence of liquid inside the pipe 21. In other words, the key point of the present invention is that "the wave propagating in the liquid must reach the ultrasonic sensor after the pipe wall propagating wave C1a has finished converging." This condition varies depending on the material of the pipe 21, the frequency of the ultrasonic waves, the inner diameter of the pipe 21, the liquid quality, etc., but unless the constants are set to always satisfy the above condition, determination is not possible.

[0051] (10) Calculation Formulas for Various Times Various times are calculated with reference to FIG.

[0052] The arrival time tps [μs] of the tube wall propagation wave C1a is expressed by the following equation 1.

[0053] tps=(π·R) / 2·(1 / Vp) Equation 1 The arrival time tls [μs] of the direct wave C2a of the wave propagating in the liquid is expressed by the following Equation 1.

[0054] tls1=(2d / Vp)+(r / Vl) Equation 2 Here, for convenience, the arrival time tps is assumed to be the time propagated on the surface of the pipe.

[0055] When the relationship tps<tls1<tpe holds, it is difficult to distinguish between the pipe wall propagating wave C1a and the direct wave C2a propagating in the liquid.

[0056] The arrival time tls3 [μs] of the TTE wave C3a of the liquid-propagating wave is expressed by the following equation 3.

[0057] tls3=(2d / Vp)+(r / Vl)·3 Equation 3 Here, the arrival time tls3 is the arrival time of the ultrasonic wave reflected at the interface between the inner circumferential surface of the pipe wall of the pipe 21 and the liquid.

[0058] When the relationship tpe<tls3 holds, the pipe wall propagation wave C1a and the TTE wave C3a propagating in the liquid can be easily distinguished.

[0059] In the present invention, tps<tls1<tpe and tpe<tls3.

[0060] As described above, in this specification, if the outer diameter of the pipe 21 is R, the inner diameter of the pipe 21 is r, the thickness of the pipe 21 is d, the propagation speed of the ultrasonic wave traveling inside the pipe 21 is Vp, and the propagation speed of the ultrasonic wave traveling through the liquid inside the pipe 21 is Vl, then the time to propagate through the pipe wall of the pipe 21 is defined as tps, the time to propagate one way through the liquid inside the pipe 21 is defined as tls1, the time to make one round trip inside the pipe 21 is defined as tls2, and the time to propagate one round trip and one way inside the pipe 21 (the propagation time of the TTE wave C3a) is defined as tls3. Furthermore, the time at which the received ultrasonic waves converge is defined as tpe, and tpe - tps is defined as the ringing time, tprin.

[0061] (11) Calculation example A calculation example is shown below. In this example, R = 18 [mm], r = 12 [mm], d = 3 [mm], VP = 5500 [m / s], Vl = 1500 [m / s], and the convergence time of the pipe-propagated wave tprin = 15 [μs].

[0062] (11-1) Calculation of the arrival time of the pipe wall propagating wave C1a The time tps [μs] at which the sound wave (pipe wall propagating wave C1a) propagating along the propagation path C1 arrives (i.e., the arrival time of the pipe wall propagating wave) is calculated using the following formula 1 (see Figure 3).

[0063] tps=(π·R) / 2·(1 / Vp)=5.1 [μs] (Equation 1) Here, for convenience, the arrival time tps is set to the arrival time of the sound wave propagating on the surface of the pipe 21.

[0064] When the convergence time tprin of the pipe wall propagation wave C1a is 15 [μs], the convergence time tpe of the pipe wall propagation wave C1a is calculated by the following formula 2.

[0065] tpe = tps + tprin = 5.1 [μs] + 15 [μs] = 20.1 [μs] Calculation formula 2 (11-2) Calculation of arrival time of submerged wave Next, the arrival time tls1 of the submerged wave direct wave C2a is the time when the sound wave propagating along propagation path C2 arrives, and is given by the following calculation formula 3 (see Figure 4).

[0066] tls1 = (2d / Vp) + (r / Vl) = 9.1 [μs] ... Calculation Formula 3 (11-3) The relationship between the arrival time tps of the pipe wall propagating wave C1a and the arrival time tls1 of the submerged propagating wave direct wave C2a is tps < tls1 ≦ tpe, and it is difficult to distinguish between the pipe wall propagating wave C1a and the submerged propagating wave direct wave C2a. For this reason, the present invention utilizes the TTE wave C3a. An example of this case is as follows.

[0067] The arrival time tls3 [μs] of the TTE wave C3a of the liquid-propagating wave is calculated by the following formula 4 (see FIG. 4).

[0068] tls3 = (2d / Vp) + (r / Vl)·3 = 25.1 [μs] (Equation 4) Here, tls3 is the reception time of the ultrasonic wave reflected at the interface between the inner surface of the pipe wall of the pipe 21 and the liquid.

[0069] tprin<tls3, and the pipe wall propagation wave C1a and the TTE wave C3a propagating in the liquid can be easily distinguished.

[0070] (12) Effects The liquid detection system 1 according to the first embodiment includes a first ultrasonic oscillator 3, a drive circuit 4, a second ultrasonic oscillator 5, a detection circuit 6, and an output unit 7a. The first ultrasonic oscillator 3 is attached to a metal pipe 21 that is the measurement target. The drive circuit 4 causes the first ultrasonic oscillator 3 to emit ultrasonic waves. The second ultrasonic oscillator 5 is attached to the pipe 21 on the opposite side from the first ultrasonic oscillator 3, and receives the ultrasonic TTE waves C3a emitted from the first ultrasonic oscillator 3. The detection circuit 6 detects the received waveform of the TTE waves C3a received by the second ultrasonic oscillator 5. The output unit 7a outputs waveform information related to the received waveform of the TTE waves C3a detected by the detection circuit 6.

[0071] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be determined with high accuracy based on the received waveform of the TTE wave C3a.

[0072] In the liquid detection system 1 according to the first embodiment, at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 is attached to the outer surface 21 a of the pipe 21 .

[0073] According to this configuration, at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 can be attached to the piping 21 without invasively inserting the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 into the piping 21. Furthermore, the degree of freedom in the location where at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 is attached can be improved.

[0074] (13) Forms Other Than Liquid Detection System Functions similar to those of the liquid detection system 1 according to the first embodiment may be realized in a liquid detection method.

[0075] A liquid detection method according to one aspect includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a first ultrasonic transducer 3 is attached to a metal pipe 21 to be measured. In the second step, an ultrasonic wave is generated from the first ultrasonic transducer 3 by a drive circuit 4. In the third step, a second ultrasonic transducer 5 is attached to the pipe 21 on the opposite side from the first ultrasonic transducer 3, and the second ultrasonic transducer 5 receives the ultrasonic TTE wave C3a generated from the first ultrasonic transducer 3. In the fourth step, a detection circuit 6 detects the received waveform of the ultrasonic TTE wave C3a received by the second ultrasonic transducer 5. In the fifth step, waveform information related to the received waveform of the TTE wave C3a detected by the detection circuit 6 is output from an output unit 7a.

[0076] (14) Modifications Modifications of the first embodiment will be described. The following modifications can be implemented in combination.

[0077] (14-1) Modification 1 In the first embodiment, the user determines whether or not there is a liquid in the pipe 21 based on the detection result of the detection circuit 6 output from the processor 7 (for example, the detection result of the detection circuit 6 output to the output unit 7a). However, the processor 7 may determine whether or not there is a liquid in the pipe 21 based on the detection result of the detection circuit 6 and output the determination result to the output unit 7a.

[0078] (14-2) Modification 2 As shown in Fig. 8, in Modification 2, the outer surface 21a of the pipe 21 has at least one of flat surfaces 21d and 21e (both flat surfaces 21d and 21e in the example of Fig. 8). The flat surface 21d is a portion where the first ultrasonic vibrator 3 is disposed. The flat surface 21e is a portion where the second ultrasonic vibrator 5 is disposed. In Modification 2, the contact surface 3a of the first ultrasonic vibrator 3 and the contact surface 5a of the second ultrasonic vibrator 5 are both flat surfaces.

[0079] The flat surface portion 21d is a part of the outer surface 21a of the pipe 21 that is formed flat. The first ultrasonic vibrator 3 is disposed with the flat contact surface 3a facing the flat surface portion 21d. Since the contact surface 3a and the flat surface portion 21d are disposed opposite each other in this manner, the first ultrasonic vibrator 3 can be attached in surface contact with the outer surface 21a of the pipe 21.

[0080] The flat surface portion 21e is another part of the outer surface 21a of the pipe 21 that is formed flat. The second ultrasonic vibrator 5 is disposed with the flat contact surface 5a facing the flat surface portion 21e. Because the contact surface 5a and the flat surface portion 21e are disposed opposite each other in this manner, the second ultrasonic vibrator 5 can be attached in surface contact with the outer surface 21a of the pipe 21.

[0081] In the liquid detection system 1 according to the second modification, the outer surface 21a of the pipe 21 has flat surfaces 21d and 21e. The first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 is disposed on the flat surfaces 21d and 21e. With this configuration, the first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 can be easily bonded to the outer surface 21a (flat surfaces) of the pipe 21. This facilitates the propagation of ultrasonic waves between the first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 and the pipe 21, thereby improving the detection accuracy of the detection circuit 6.

[0082] (14-3) Modification 3 As shown in Fig. 9, the liquid detection system 1 according to Modification 3 further includes at least one of spacers 30 and 31 (both spacers 30 and 31 in the example of Fig. 9). The spacer 30 is a member disposed between the convex curved surface portion of the outer surface 21a of the pipe 21 and the first ultrasonic transducer 3. The spacer 31 is a member disposed between the convex curved surface portion of the outer surface 21a of the pipe 21 and the second ultrasonic transducer 5. In Modification 3, the contact surface 3a of the first ultrasonic transducer 3 and the contact surface 5a of the second ultrasonic transducer 5 are both flat surfaces.

[0083] More specifically, the spacer 30 is formed of resin or metal. The spacer 30 has a concave surface portion 30a and a flat surface portion 31b. The concave surface portion 30a is a portion that fits into the convex surface portion of the outer surface 21a of the pipe 21. The flat surface portion 30b is a portion where the first ultrasonic transducer 3 is disposed. The flat surface portion 30b is a flat surface and is the surface of the spacer 30 opposite the concave surface portion 30a. The concave surface portion 30a of the spacer 30 is in surface contact with the outer surface 21a of the pipe 21. The flat surface portion 30b of the spacer 30 faces and contacts the contact surface 3a of the first ultrasonic transducer 3. Therefore, the spacer 30 can fill the gap between the first ultrasonic transducer 3 and the outer surface 21a of the pipe 21. This facilitates propagation of ultrasonic waves between the first ultrasonic transducer 3 and the pipe 21.

[0084] The spacer 31 is formed in the same manner as the spacer 30. That is, the spacer 31 is formed of resin or metal. The spacer 31 has a concave surface portion 31a and a flat surface portion 31b. The concave surface portion 31a is a portion that fits into the convex surface portion of the outer surface 21a of the pipe 21. The flat surface portion 31b is a portion where the second ultrasonic transducer 5 is disposed. The flat surface portion 31b is a flat surface and is the surface of the spacer 31 opposite the concave surface portion 31a. The concave surface portion 31a of the spacer 31 is in surface contact with the outer surface 21a of the pipe 21. The flat surface portion 31b of the spacer 31 faces and contacts the contact surface 3a of the second ultrasonic transducer 5. Therefore, the spacer 31 can fill the gap between the second ultrasonic transducer 5 and the outer surface 21a of the pipe 21. This facilitates propagation of ultrasonic waves between the second ultrasonic transducer 5 and the pipe 21.

[0085] The liquid detection system 1 according to the third modification further includes spacers 30, 31. The spacers 30, 31 are disposed between the first ultrasonic transducer 3 or the second ultrasonic transducer 5 and the convex curved surface portion of the outer surface 21a of the pipe 21. The spacers 30, 31 have concave curved surface portions 30a, 31a and flat surface portions 30b, 31b. The concave curved surface portions 30a, 31a fit into the convex curved surface portion of the pipe 21. The first ultrasonic transducer 3 or the second ultrasonic transducer 5 is disposed on the flat surface portions 30b, 31b.

[0086] According to this configuration, the spacers 30, 31 can fill the gap between the first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 and the convex curved portion of the outer surface 21a of the pipe 21. This makes it easier for ultrasonic waves to propagate between the first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 and the pipe 21, thereby improving the detection accuracy of the detection circuit 6.

[0087] (14-4) Modification 4 As shown in FIG. 10, in modification 4, at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 (both in the example of FIG. 10) is embedded in the metal part 21b of the pipe 21.

[0088] More specifically, the metal portion 21b of the pipe 21 has storage portions 21f and 21g. The storage portion 21f is a hollow portion for embedding the first ultrasonic vibrator 3 in the metal portion 21b. The storage portion 21g is a hollow portion for embedding the second ultrasonic vibrator 5 in the metal portion 21b. The thickness d1 of the portion of the metal portion 21b where the storage portions 21f and 21g are provided is thicker than the thickness d3 of the remaining portion. This ensures a thickness sufficient to secure the storage portions 21f and 21g within the metal portion 21b.

[0089] The storage sections 21f, 21g are arranged inside the metal section 21b, sandwiching the hollow section 21c of the pipe 21. That is, the storage sections 21f, 21g are arranged side by side in the diameter direction of the pipe 21. The storage sections 21f, 21g extend along the longitudinal direction of the pipe 21. Of both end faces of the metal section 21b in the longitudinal direction (i.e., the longitudinal direction of the pipe 21), one end face of the storage sections 21f, 21g is open and connected to the external space, and the other end face is closed and not open. The opening of each of the storage sections 21f, 21g functions as a port for inserting and removing the first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 into the storage section 21f, 21g. That is, in the fourth modification, after the pipe 21 is formed to have the storage sections 21f, 21g, the first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 is stored in the storage section 21f, 21g through the opening. By this housing, the first ultrasonic vibrator 3 or the second ultrasonic vibrator 5 is embedded in the metal part 21 b of the pipe 21 .

[0090] The cross-sectional shape of the storage sections 21f, 21g (cross-sectional shape in a cross section perpendicular to the longitudinal direction of the piping 21) is, for example, the same shape and size as the cross section of each of the first ultrasonic transducer 3 and the second ultrasonic transducer 5. As a result, the first ultrasonic transducer 3 and the second ultrasonic transducer 5 are in surface contact with the storage sections 21f, 21g when stored in the storage sections 21f, 21g (i.e., when embedded in the metal section 21b). That is, the outer surfaces of the first ultrasonic transducer 3 and the second ultrasonic transducer 5 are in surface contact with the storage sections 21f, 21g. As a result, ultrasonic waves generated from the first ultrasonic transducer 3 can be effectively propagated to the metal section 21b. Furthermore, received ultrasonic waves can be effectively propagated from the metal section 21b to the second ultrasonic transducer 5.

[0091] In the liquid detection system 1 according to the fourth modification, at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 is embedded in the metal portion 21b of the pipe 21. With this configuration, at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 can be attached closer to the hollow portion 21c of the pipe 21 than when at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 is attached to the outer surface 21a of the pipe 21. As a result, the detection accuracy of the detection circuit 6 can be improved. Furthermore, at least one of the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 can be protected by the metal portion 21b of the pipe 21.

[0092] (14-5) Modification 5 As shown in Fig. 11, in Modification 5, the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 are each fixed to the outer surface 21a of the pipe 21 by fasteners 40 (also called clamps). In the example of Fig. 11, the case where two fasteners 40 are used is illustrated, but at least one of the two fasteners 40 may be used.

[0093] The fastener 40 has a main body 41, a pressing portion 42, a screw portion 43, and a handle portion 44. The main body 41 has a U-shape. The contact surface 41a of the main body 41 is one end of the inner surface of the main body 41 and is the portion that contacts one of the top surfaces of the first ultrasonic transducer 3 and the second ultrasonic transducer 5 (the top surface 3s of the first ultrasonic transducer 3 in the example of FIG. 11). A screw hole 41b is provided through the other end of the main body 41. A screw portion 43 is screwed into the screw hole 41b. The pressing portion 42 is the portion that is pressed against the other top surface of the first ultrasonic transducer 3 and the second ultrasonic transducer 5 (the top surface 5s of the second ultrasonic transducer 5 in the example of FIG. 11). The pressing portion 42 has a contact surface 42a and a back surface 42b. The contact surface 42a is the surface that contacts the top surface 5s of the second ultrasonic transducer 5. The back surface 42b is the main surface of the pressing portion 42 opposite to the contact surface 41a. The threaded portion 43 is rotatably connected to the pressing portion 42 and protrudes from the back surface 42b of the pressing portion 42. The threaded portion 43 is screwed through the threaded hole 41b of the main body 41. The handle portion 44 is a portion for manually rotating the threaded portion 43. The handle portion 44 protrudes from the end of the threaded portion 43 in the radial direction of the threaded portion 43.

[0094] The fastener 40 positions the pipe 21, on which the first ultrasonic vibrator 3 and the second ultrasonic vibrator 5 are disposed, between the contact surface 41 a of the main body 41 and the pressing portion 42. Then, by operating the handle portion 44 and rotating the screw portion 43 so as to screw it into the screw hole 41 b, the pressing portion 42 presses against the top surface 5 s of the second ultrasonic vibrator 5. As a result, the first ultrasonic vibrator 3 is sandwiched and fixed between the contact surface 41 a of the main body 41 and the outer surface 21 a of the pipe 21. Furthermore, the second ultrasonic vibrator 5 is sandwiched and fixed between the pressing portion 42 and the outer surface 21 a of the pipe 21.

[0095] Second Embodiment A liquid detection system 1 according to a second embodiment will be described with reference to FIG.

[0096] 12 , the liquid detection system 1 according to the second embodiment is configured in the same manner as the liquid detection system 1 according to the first embodiment, except that it uses one ultrasonic vibrator 10 to emit and receive ultrasonic waves, and that it uses QTE (Quadruple Transit Echo) waves instead of TTE waves to determine the presence or absence of liquid in the pipe 21. Hereinafter, the same components as those in the liquid detection system 1 according to the first embodiment will be assigned the same reference numerals and their description will be omitted, and the following description will focus on the components that are different from those in the liquid detection system 1 according to the first embodiment.

[0097] The liquid detection system 1 according to the second embodiment includes an ultrasonic vibrator 10, a drive circuit 4, a detection circuit 6B, a damping circuit 11, a switching circuit 12, and a processor 7.

[0098] The drive circuit 4 and the detection circuit 6B are configured in the same manner as the drive circuit 4 and the detection circuit 6 of the first embodiment, and therefore detailed description thereof will be omitted.

[0099] The ultrasonic transducer 10 serves as both an ultrasonic transducer for oscillation and an ultrasonic transducer for reception. The ultrasonic transducer 10 is configured similarly to the first ultrasonic transducer 3 and the second ultrasonic transducer 5 of the first embodiment. The ultrasonic transducer 10 is attached to the outer surface 21a of the pipe 21 to be measured. When the ultrasonic transducer 10 is electrically connected to the drive circuit 4 and receives a drive signal of a first frequency from the drive circuit 4, the ultrasonic transducer 10 oscillates ultrasonic waves of a second frequency, similar to the first ultrasonic transducer 3 of the first embodiment. Furthermore, when the ultrasonic transducer 10 is electrically connected to the detection circuit 6B, the ultrasonic transducer 10 generates an electrical signal corresponding to the waveform of the received ultrasonic waves (DTE (Double Transit Echo) waves and QTE waves), similar to the second ultrasonic transducer 5 of the first embodiment, and outputs the generated electrical signal to the detection circuit 6B as a received wave.

[0100] The ultrasonic transducer 10 is configured in the same manner as the first ultrasonic transducer 3 and the second ultrasonic transducer 5 of the first embodiment. That is, the ultrasonic transducer 10 has, for example, a rectangular parallelepiped outer shape and has a contact surface 10a that contacts the outer surface 21a of the pipe 21. The contact surface 10a has a concave curved portion with the same curved shape as the convex curved portion of the outer surface 21a of the pipe 21. The ultrasonic transducer 10 is attached to the outer surface 21a with, for example, an adhesive. When the ultrasonic transducer 10 is electrically connected to the drive circuit 4 and receives a drive signal from the drive circuit 4, it emits ultrasonic waves from the contact surface 3a. When the ultrasonic transducer 10 is electrically connected to the detection circuit 6B, it generates an electrical signal corresponding to the waveform of the received ultrasonic wave and outputs the generated electrical signal to the detection circuit 6B as a received wave.

[0101] The damping circuit 11 is electrically connected to the ultrasonic transducer 10, thereby suppressing reverberation after the ultrasonic waves are oscillated in the ultrasonic transducer 10. The damping circuit 11 is, for example, a damping resistor.

[0102] The switching circuit 12 selectively switches the connection partner of the ultrasonic transducer 10 from among the drive circuit 4, the detection circuit 6B, and the damping circuit 11. The switching circuit 12 switches the connection partner of the ultrasonic transducer 10 under the control of the processor 7.

[0103] More specifically, the switching circuit 12 switches the connection partners of the ultrasonic transducer 10 in the order of the drive circuit 4, the damping circuit 11, and the detection circuit 6B. That is, the switching circuit 12 first electrically connects the ultrasonic transducer 10 to the drive circuit 4. With this connection, the ultrasonic transducer 10 functions as an ultrasonic transducer for oscillation. Then, as in the case of embodiment 1, a drive signal from the drive circuit 4 is input to the ultrasonic transducer for oscillation 10, causing the ultrasonic transducer for oscillation 10 to emit ultrasonic waves. Then, the switching circuit 12 separates the ultrasonic transducer 10 from the drive circuit 4 and electrically connects it to the damping circuit 11. With this connection, the damping circuit 11 suppresses reverberation after the ultrasonic transducer 10 emits ultrasonic waves. This suppresses the influence of reverberation after the ultrasonic transducer 10 emits ultrasonic waves on the reception of ultrasonic waves by the ultrasonic transducer 10.

[0104] The switching circuit 12 then separates the ultrasonic transducer 10 from the damping circuit 11 and electrically connects it to the detection circuit 6B. This connection causes the ultrasonic transducer 10 to function as a receiving ultrasonic transducer. The detection circuit 6B detects the received waveforms (DTE waves and QTE waves) of the ultrasonic waves received by the receiving ultrasonic transducer 10.

[0105] The switching circuit 12 has a common terminal 12a and a plurality of (three in the example of FIG. 12 ) selection terminals 12b, 12c, and 12d. The common terminal 12a is selectively connected to the plurality of selection terminals 12b, 12c, and 12d. The common terminal 12a is connected to the ultrasonic transducer 10. The selection terminal 12b is connected to the drive circuit 4. The selection terminal 12c is connected to the damping circuit 11. The selection terminal 12d is connected to the detection circuit 6B. When the common terminal 12a is connected to the selection terminal 12b, the ultrasonic transducer 10 is connected to the drive circuit 4. When the common terminal 12a is connected to the selection terminal 12c, the ultrasonic transducer 10 is connected to the damping circuit 11. When the common terminal 12a is connected to the selection terminal 12d, the ultrasonic transducer 10 is connected to the detection circuit 6B.

[0106] The processor 7 further performs an operation of controlling the switching circuit 12 in the operation of the processor 7 of embodiment 1. More specifically, when the ultrasonic transducer 10 is to emit ultrasonic waves, the processor 7 controls the switching circuit 12 to connect the ultrasonic transducer 10 to the drive circuit 4. After this control, the processor 7 outputs a control signal to the drive circuit 4 for emitting ultrasonic waves from the ultrasonic transducer 10. After this output, the processor 7 controls the switching circuit 12 to connect the ultrasonic transducer 10 to the damping circuit 11. After this control, the processor 7 controls the switching circuit 12 to connect the ultrasonic transducer 10 to the detection circuit 6B.

[0107] (2) How Ultrasonic Waves Propagate in a Pipe The propagation of ultrasonic waves in the pipe 21 to be measured will be described with reference to FIG.

[0108] As shown in FIG. 12 , in the liquid detection system 1 according to the second embodiment, the ultrasonic vibrator 10 is disposed on the outer surface 21 a of the pipe 21 .

[0109] 12 is a propagation path of a propagation wave (pipe wall one-circumference propagation wave C4Aa) that propagates around the pipe wall (metal part 21b) of pipe 21 once. Propagation path C4B in FIG. 12 is a propagation path of a propagation wave (pipe wall two-circumference propagation wave C4Ba) that propagates around the pipe wall of pipe 21 twice. Propagation path C5 in FIG. 2 is a propagation path of a propagation wave (DTE wave C5a) that propagates through the liquid inside pipe 21 (hollow part 21c) by making two round trips. Propagation path C6 in FIG. 2 is a propagation path of a propagation wave (QTE wave 6a) that propagates through the liquid inside pipe 21 by making two round trips. In FIG. 12, the pipe wall one-circumference propagation wave C4Aa and the pipe wall two-circumference propagation wave C4Ba are depicted as if they are propagating inside the pipe 21 for convenience of illustration, but in reality they propagate on the outer surface of the pipe 21.

[0110] When there is no liquid in the hollow portion 21c of the pipe 21, most of the ultrasonic waves emitted from the ultrasonic vibrator 10 propagate circumferentially around the metal portion 21b of the pipe 21 as a pipe wall one-circumference wave C4Aa and a pipe wall two-circumference wave C4Ba, as shown in propagation paths C4A and C4B, and are received by the ultrasonic vibrator 10. The pipe wall one-circumference wave C4Aa is emitted from the ultrasonic vibrator 10, propagates around the metal portion 21b of the pipe 21 in the circumferential direction, and is received by the ultrasonic vibrator 10. The pipe wall two-circumference wave C4Ba is emitted from the ultrasonic vibrator 10, propagates around the metal portion 21b of the pipe 21 in the circumferential direction, and is received by the ultrasonic vibrator 10. In this case, the ultrasonic waves emitted from the ultrasonic vibrator 10 are hardly propagated through the air in the hollow portion 21c of the pipe 21. Furthermore, the wave C4Aa that propagates around the pipe wall once travels around the metal portion 21b before the ultrasonic vibrator 10 switches from oscillation to reception, and therefore cannot be received by the ultrasonic vibrator 10. For this reason, as shown in Figure 13, when there is no liquid in the hollow portion 21c of the pipe 21, only the waveform of the wave C4Ba that propagates around the pipe wall twice appears in the received waveform of the ultrasonic vibrator 10 (the detection result of the detection circuit 6B). In the example of Figure 13, the wave C4Ba that propagates around the pipe wall twice appears in the section of approximately 20 μs to 25 μs.

[0111] When liquid is present in the hollow portion 21c of the pipe 21, the ultrasonic waves emitted from the ultrasonic vibrator 10 propagate circumferentially through the metal portion 21b of the pipe 21 as a pipe wall one-circumference propagation wave C4Aa and a pipe wall two-circumference propagation wave C4Ba, as shown in propagation paths C4A and C4B, and are received by the ultrasonic vibrator 10. In this case, the ultrasonic waves emitted from the ultrasonic vibrator 10 further propagate through the liquid in the hollow portion 21c of the pipe 21 as a DTE wave C5a (propagation path C5) and a QTE wave C6a (propagation path C6), and are received by the ultrasonic vibrator 10. The DTE wave C5a travels back and forth once in the diameter direction of the pipe 21 by being reflected by the inner surface of the pipe 21 through the liquid in the hollow portion 21c of the pipe 21, and is received by the ultrasonic vibrator 10. The QTE wave C6a travels back and forth twice in the diameter direction of the pipe 21 by being reflected by the inner surface of the pipe 21 through the liquid in the hollow portion 21c of the pipe 21, and is received by the ultrasonic transducer 10.

[0112] 14, when liquid is present in the cavity 21c of the pipe 21, the received waveform of the ultrasonic transducer 10 (detection result of the detection circuit 6B) includes the waveforms of the pipe wall double-circuiting wave C4Ba, the DTE wave C5a, and the QTE wave C6a. Because the pipe wall double-circuiting wave C4Ba and the DTE wave C5a have almost the same propagation time, the waveforms of the pipe wall double-circuiting wave C4Ba and the DTE wave C5a appear overlapping each other. Compared to the DTE wave C5a, the QTE wave C6a propagates one extra round trip through the liquid in the cavity 21c in the diameter direction of the pipe 21. Therefore, the QTE wave C6a appears with a certain delay from the waveform of the DTE wave C5a. In the example of Figure 14, the tube wall double propagation wave C4Ba and the DTE wave C5a appear in the interval of approximately 15 μs to 25 μs, and the QTE wave C6a appears in the interval of approximately 35 μs to 45 μs.

[0113] 13 and 14, the received waveforms (received frequency range and received intensity) of the wave C4Ba that propagates twice around the pipe wall and the DTE wave C5a when there is liquid in the cavity 21c of the pipe 21 (FIG. 13) are almost the same as the received waveform of the wave C4Ba that propagates twice around the pipe wall when there is no liquid in the cavity 21c of the pipe 21 (FIG. 14). For this reason, it is difficult to determine the presence or absence of liquid in the pipe 21 based on the received waveforms of the wave C4Ba that propagates twice around the pipe wall and the DTE wave C5a among the waves received by the ultrasonic vibrator 10.

[0114] 13 and 14, when there is no liquid in the hollow portion 21c of the pipe 21 (FIG. 13), the received waveform of the QTE wave C6a hardly appears, but when there is liquid in the hollow portion 21c of the pipe 21 (FIG. 14), the received waveform of the QTE wave C6a appears with a sufficient delay from the pipe wall double-propagation wave C4Ba and the DTE wave C5a. Therefore, it is possible to determine the presence or absence of liquid in the pipe 21 based on the received waveform of the QTE wave C6a among the waves received by the ultrasonic transducer 10.

[0115] (3) Principle of Determining the Presence or Absence of Liquid in a Pipe As described above, it is difficult to determine the presence or absence of liquid in the pipe 21 based on the received waveforms of the pipe wall double-propagation wave C4Ba and the DTE wave C5a among the waves received by the ultrasonic transducer 10. However, it is easy to determine the presence or absence of liquid in the pipe 21 based on the received waveform of the QTE wave C6a among the waves received by the ultrasonic transducer 10. For this reason, in the liquid detection system 1, the user determines the presence or absence of liquid in the pipe 21 based on the received waveform of the QTE wave C6a received by the ultrasonic transducer 10. More specifically, if the received waveform of the QTE wave C6a is included in the waves received by the ultrasonic transducer 10, it is determined that liquid is present in the pipe 21. On the other hand, if the received waveform of the QTE wave C6a is not included in the waves received by the ultrasonic transducer 10, it is determined that no liquid is present in the pipe 21.

[0116] (4) Effects The liquid detection system 1 according to the second embodiment includes an ultrasonic transducer 10, a drive circuit 4, a detection circuit 6B, a switching circuit 12, and a processor 7. The ultrasonic transducer 10 is attached to a metal pipe 21 that is the measurement target. The drive circuit 4 is connected to the ultrasonic transducer 10 and causes the ultrasonic transducer 10 to emit ultrasonic waves. The detection circuit 6B is connected to the ultrasonic transducer 10 and detects the received waveform of the QTE wave C6a of the ultrasonic waves received by the ultrasonic transducer 10. The switching circuit 12 connects the ultrasonic transducer 10 to the drive circuit 4, and then separates the ultrasonic transducer 10 from the drive circuit 4 and connects it to the detection circuit 6B. The processor 7 outputs waveform information related to the received waveform of the QTE wave C6a detected by the detection circuit 6B.

[0117] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be accurately determined based on the received waveform of the QTE wave C6a output from the processor 7. Furthermore, since ultrasonic waves are emitted and received by a single ultrasonic vibrator 10, the work of attaching the ultrasonic vibrator 10 to the pipe 21 can be reduced, and costs can also be reduced.

[0118] The liquid detection system 1 according to the second embodiment also includes a damping circuit 11. The damping circuit 11 is connected to the ultrasonic transducer 10 and suppresses reverberation after the ultrasonic transducer 10 generates ultrasonic waves. The switching circuit 12 switches the connection of the ultrasonic transducer 10 between the drive circuit 4, the damping circuit 11, and the detection circuit 6B in that order.

[0119] According to this configuration, the damping circuit 11 can prevent reverberation after the ultrasonic wave is generated in the ultrasonic transducer 10 from being mixed into the received wave of the ultrasonic transducer 10. As a result, the detection accuracy of the QTE wave C6a by the detection circuit 6B can be improved.

[0120] Furthermore, in the liquid detection system 1 according to the second embodiment, the ultrasonic vibrator 10 is attached to the outer surface 21a of the pipe 21. According to this configuration, the ultrasonic vibrator 10 can be attached to the pipe 21 without invasively inserting the ultrasonic vibrator 10 into the pipe 21. Furthermore, the degree of freedom in the installation location of the ultrasonic vibrator 10 can be improved.

[0121] (5) Forms Other Than Liquid Detection System Functions similar to those of the liquid detection system 1 according to the second embodiment may be realized in a liquid detection method.

[0122] A liquid detection method according to one aspect includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, an ultrasonic transducer 10 is attached to a metal pipe 21 to be measured. In the second step, an ultrasonic wave is emitted from the ultrasonic transducer 10 by the drive circuit 4. In the third step, a received waveform of the ultrasonic wave received by the ultrasonic transducer 10 is detected by the detection circuit 6B. In the fourth step, the ultrasonic transducer 10 is connected to the drive circuit 4, and then the ultrasonic transducer 10 is separated from the drive circuit 4 and connected to the detection circuit 6B. In the fifth step, waveform information regarding the received waveform of the QTE wave C6a detected by the detection circuit 6B is output.

[0123] (6) Modifications A description will be given of modifications of the second embodiment. In the second embodiment, modifications similar to the first to fifth modifications of the first embodiment may also be implemented.

[0124] Third Embodiment (1) Configuration A liquid detection system 1 according to a third embodiment will be described with reference to FIG.

[0125] 15 , the liquid detection system 1 according to the third embodiment is configured in the same manner as the liquid detection system 1 according to the second embodiment, except that the ultrasonic vibrator 10 for both oscillation and reception is separated into a first ultrasonic vibrator 15 for oscillation and a second ultrasonic vibrator 16 for reception. In the following, the same components as those in the liquid detection systems 1 according to the first and second embodiments are denoted by the same reference numerals and a description thereof will be omitted, and the following description will focus on the components that are different from those in the liquid detection systems 1 according to the first and second embodiments.

[0126] As shown in FIG. 15, the liquid detection system 1 according to the third embodiment includes a first ultrasonic vibrator 15, a second ultrasonic vibrator 16, a driving circuit 4, a detection circuit 6C, a damping circuit 11, and a processor 7.

[0127] The drive circuit 4, detection circuit 6C, damping circuit 11 and processor 7 are configured in the same manner as the drive circuit 4, detection circuit 6B, damping circuit 11 and processor 7 of embodiment 2, and therefore their description will be omitted.

[0128] The first ultrasonic vibrator 15 is an ultrasonic vibrator for oscillation that is attached to the metal pipe 21 that is the measurement target and emits ultrasonic waves. The first ultrasonic vibrator 15 has the same configuration as the first ultrasonic vibrator 3 of embodiment 1, and is attached to the outer surface 21a of the pipe 21 in the same manner as the first ultrasonic vibrator 3 of embodiment 1. Therefore, a detailed description of the first ultrasonic vibrator 15 will be omitted.

[0129] The second ultrasonic transducer 16 is attached around the first ultrasonic transducer on the outer surface 21a of the metal pipe 21 to be measured. In the example of Fig. 15, the second ultrasonic transducer 16 is adjacent to the first ultrasonic transducer 15 in the circumferential direction of the pipe 21, but may be adjacent to the first ultrasonic transducer 15 in the longitudinal direction of the pipe 21 (the direction perpendicular to the plane of the drawing). The second ultrasonic transducer 16 is a receiving ultrasonic transducer that receives ultrasonic waves. The second ultrasonic transducer 16 receives ultrasonic waves emitted from the first ultrasonic transducer 3. The second ultrasonic transducer 16 is configured similarly to the second ultrasonic transducer 5 of the first embodiment. When the second ultrasonic transducer 16 receives ultrasonic waves from the first ultrasonic transducer 3, it generates an electrical signal corresponding to the waveform of the received ultrasonic waves and outputs the generated electrical signal to the detection circuit 6C as a received wave.

[0130] The switching circuit 17 selectively switches the connection partner of the first ultrasonic transducer 15 between the drive circuit 4 and the damping circuit 11. The switching circuit 17 switches the connection partner of the first ultrasonic transducer 15 under the control of the processor 7. Note that the switching of the switching circuit 17 may be performed manually.

[0131] More specifically, under the control of the processor 7, the switching circuit 17 switches the connection partner of the first ultrasonic transducer 15 between the drive circuit 4 and the damping circuit 11, in that order. That is, the switching circuit 17 first connects the first ultrasonic transducer 15 to the drive circuit 4. With this connection, a drive signal from the drive circuit 4 is input to the first ultrasonic transducer 15, causing the first ultrasonic transducer 15 to emit ultrasonic waves. Then, the switching circuit 17 separates the first ultrasonic transducer 15 from the drive circuit 4 and connects it to the damping circuit 11. With this connection, the damping circuit 11 suppresses reverberation after the oscillation of ultrasonic waves in the first ultrasonic transducer 15. This makes it possible to suppress reverberation after the oscillation of ultrasonic waves in the first ultrasonic transducer 15 from affecting the reception of ultrasonic waves by the second ultrasonic transducer 16.

[0132] The switching circuit 17 has a common terminal 17a and a plurality of (two in the example of FIG. 15 ) selection terminals 17b, 17c. The common terminal 17a is selectively connected to the plurality of selection terminals 17b, 17c. The common terminal 17a is connected to the first ultrasonic transducer 15. The selection terminal 17b is connected to the drive circuit 4. The selection terminal 17c is connected to the damping circuit 11. When the common terminal 17a is connected to the selection terminal 17b, the first ultrasonic transducer 15 is connected to the drive circuit 4. When the common terminal 17a is connected to the selection terminal 17c, the first ultrasonic transducer 15 is electrically connected to the damping circuit 11.

[0133] The processor 7 further performs an operation of controlling the switching circuit 17 in the operation of the processor 7 of embodiment 1. More specifically, when ultrasonic waves are to be oscillated from the ultrasonic transducer 10, the processor 7 controls the switching circuit 17 to connect the first ultrasonic transducer 15 to the drive circuit 4. After this control, the processor 7 outputs a control signal to the drive circuit 4 for oscillating ultrasonic waves from the first ultrasonic transducer 15. After this output, the processor 7 controls the switching circuit 12 to connect the ultrasonic transducer 10 to the damping circuit 11. Then, when the detection result of the detection circuit 6C is input to the processor 7, the processor 7 outputs the input detection result to the output unit 7a.

[0134] (2) Effects The liquid detection system 1 according to the third embodiment includes a first ultrasonic oscillator 15, a drive circuit 4, a second ultrasonic oscillator 16, a detection circuit 6C, and a processor 7. The first ultrasonic oscillator 15 is attached to a metal pipe 21 that is the measurement target. The drive circuit 4 causes the first ultrasonic oscillator 15 to emit ultrasonic waves. The second ultrasonic oscillator 16 is attached to the periphery of the first ultrasonic oscillator 15 in the pipe 21 and receives the ultrasonic QTE wave C6a emitted from the first ultrasonic oscillator 15. The detection circuit 6C detects the received waveform of the ultrasonic QTE wave C6a received by the second ultrasonic oscillator 5. The processor 7 outputs waveform information related to the received waveform of the QTE wave C6a detected by the detection circuit 6C.

[0135] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be accurately determined based on the received waveform of the QTE wave C6a output from the processor 7. Furthermore, since the ultrasonic transducers 15 and 16 do not switch between emitting and receiving ultrasonic waves, the processing load can be reduced.

[0136] Furthermore, the liquid detection system 1 according to the third embodiment includes a damping circuit 11. The damping circuit 11 suppresses reverberation after the ultrasonic wave is generated in the first ultrasonic oscillator 15. According to this configuration, the damping circuit 11 can suppress reverberation after the ultrasonic wave is generated in the first ultrasonic oscillator 15 from being mixed into the received wave of the second ultrasonic oscillator 16. As a result, the detection accuracy of the QTE wave C6a by the detection circuit 6C can be improved.

[0137] (3) Forms Other Than Liquid Detection System Functions similar to those of the liquid detection system 1 according to the third embodiment may be realized in a liquid detection method.

[0138] A liquid detection method according to one aspect includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a first ultrasonic transducer 15 is attached to a metal pipe 21 to be measured. In the second step, ultrasonic waves are emitted from the first ultrasonic transducer 15 by the drive circuit 4. In the third step, a second ultrasonic transducer 16 is attached to the periphery of the first ultrasonic transducer 15 in the pipe 21, and the second ultrasonic transducer 16 receives the ultrasonic QTE wave C6a emitted from the first ultrasonic transducer 15. In the fourth step, the detection circuit 6C detects the received waveform of the QTE wave C6a received by the second ultrasonic transducer 16. In the fifth step, waveform information relating to the received waveform of the QTE wave C6a detected by the detection circuit 6C is output.

[0139] (4) Modifications A description will be given of modifications of the third embodiment. In the third embodiment, modifications similar to the first to fifth modifications of the first embodiment may also be implemented.

[0140] Fourth Embodiment A liquid detection system 1 according to a fourth embodiment will be described with reference to FIG.

[0141] (1) Configuration The liquid detection system 1 according to the fourth embodiment is a device that combines the liquid detection systems 1 according to the first and second embodiments. That is, the liquid detection system 1 according to the fourth embodiment can determine the presence or absence of a liquid in the pipe 21 based on the received waveforms of the DTE wave, TTE wave, and QTE wave of the ultrasonic waves emitted by the first ultrasonic vibrator 3.

[0142] 16 , the liquid detection system 1 according to embodiment 4 further includes the switching circuit 12, damping circuit 11, and detection circuit 6B of embodiment 2 in addition to the liquid detection system 1 according to embodiment 1. That is, the liquid detection system 1 according to embodiment 4 includes a first ultrasonic vibrator 3, a drive circuit 4, a second ultrasonic vibrator 5, a detection circuit 6, a processor 7, a damping circuit 11, a detection circuit 6B, and a switching circuit 12. In the following description, the detection circuit 6 of embodiment 1 will be referred to as the first detection circuit 6, and the detection circuit 6B of embodiment 2 will be referred to as the second detection circuit 6B.

[0143] The first ultrasonic vibrator 3, the drive circuit 4, the second ultrasonic vibrator 5, the first detection circuit 6, and the processor 7 are configured in the same manner as in the first embodiment, and therefore detailed descriptions thereof will be omitted. Also, the damping circuit 11, the second detection circuit 6B, and the switching circuit 12 are configured in the same manner as in the second embodiment, and therefore detailed descriptions thereof will be omitted.

[0144] In the fourth embodiment, the first ultrasonic transducer 3 serves both as an ultrasonic transducer for emitting ultrasonic waves and as an ultrasonic transducer for receiving ultrasonic waves (e.g., QTE waves) emitted by the first ultrasonic transducer 3. The first ultrasonic transducer 3 is connected to the common terminal 12a of the switching circuit 12.

[0145] The switching circuit 12 of the fourth embodiment selectively switches the connection partner of the first ultrasonic transducer 3 from among the drive circuit 4, the second detection circuit 6B, and the damping circuit 11. The switching circuit 12 switches the connection partner of the first ultrasonic transducer 3 under the control of the processor 7. Note that the switching of the switching circuit 12 may be performed manually.

[0146] (2) Operation The operation of the liquid detection system 1 according to the fourth embodiment will be described with reference to FIG.

[0147] The switching circuit 12 switches the connection partner of the first ultrasonic transducer 3 in the order of the drive circuit 4, the damping circuit 11, and the second detection circuit 6B. More specifically, the switching circuit 12 first connects the first ultrasonic transducer 3 to the drive circuit 4. With this connection, the first ultrasonic transducer 3 functions as an ultrasonic transducer for oscillation. Then, a drive signal from the drive circuit 4 is input to the first ultrasonic transducer 3, causing the first ultrasonic transducer 3 to emit ultrasonic waves. The oscillated ultrasonic waves propagate through the metal portion 21b and the hollow portion 21c of the piping 21. The oscillated ultrasonic waves then propagate as pipe wall propagating waves C1a, submerged direct propagating waves C2a, and TTE waves C3a (see FIG. 2 ) and are received by the second ultrasonic transducer 5. The oscillated ultrasonic waves propagate as a tube wall double propagation wave C4Ba, a DTE wave C5a, and a QTE wave C6a (see FIG. 12) and are received by the first ultrasonic receiving transducer 3.

[0148] Then, the switching circuit 12 separates the first ultrasonic transducer 3 from the drive circuit 4 and connects it to the damping circuit 11. This connection allows the damping circuit 11 to suppress reverberation after the oscillation of ultrasonic waves in the first ultrasonic transducer 3. This makes it possible to suppress the influence of reverberation after the oscillation of ultrasonic waves in the first ultrasonic transducer 3 for oscillation on the reception of ultrasonic waves by the first ultrasonic transducer 3 for reception.

[0149] Then, the switching circuit 12 separates the first ultrasonic transducer 10 from the damping circuit 11 and connects it to the second detection circuit 6B. With this connection, the first ultrasonic transducer 3 functions as a receiving ultrasonic transducer and receives the tube wall double-circuit propagation waves C4Ba, DTE waves C5a, and QTE waves C6a of the ultrasonic waves emitted by the first ultrasonic transducer 3. The second detection circuit 6Ba detects the received waveforms of the tube wall double-circuit propagation waves C4Ba, DTE waves C5a, and QTE waves C6a of the ultrasonic waves received by the first receiving ultrasonic transducer 3.

[0150] The second ultrasonic transducer 5 receives the tube wall propagation wave C1a, the submerged direct propagation wave C2a, and the TTE wave C3a of the ultrasonic waves emitted by the first ultrasonic transducer 3. The first detection circuit 6 detects the received waveforms of the ultrasonic waves received by the second ultrasonic transducer 5 (the tube wall propagation wave C1a, the submerged direct propagation wave C2a, and the TTE wave C3a).

[0151] The processor 7 then outputs the detection results of the first detection circuit 6 and the second detection circuit 6B to the output unit 7a. The user determines whether or not there is liquid in the pipe 21 based on the detection results of the first detection circuit 6 and the second detection circuit 6B output to the output unit 7a. For example, if at least one of the TTE wave C3a and the QTE wave C6a is detected, it is determined that there is liquid in the pipe 21, and if neither the TTE wave C3a nor the QTE wave C6a is detected, it is determined that there is no liquid in the pipe 21. Note that if both the TTE wave C3a and the QTE wave C6a are detected, it may be determined that there is liquid in the pipe 21, and if neither the TTE wave C3a nor the QTE wave C6a is detected, or if only one of the TTE wave C3a and the QTE wave C6a is detected, it may be determined that there is no liquid in the pipe 21.

[0152] Furthermore, if it is determined that there is liquid in the pipe 21, the user may further identify the type of liquid based on the TTE wave C3a and the QTE wave C6a (more specifically, based on the time difference between the received waveforms of the TTE wave C3a and the QTE wave C6a, and the change in amplitude of the TTE wave C3a and the QTE wave C6a).

[0153] (3) Effects The liquid detection system 1 according to embodiment 4 further includes a second detection circuit 6B and a switching circuit 12 in the liquid detection system 1 according to embodiment 1. The second detection circuit 6B detects the received waveform of the QTE wave C6a of the ultrasonic wave received by the first ultrasonic oscillator 3. The second detection circuit 6B is different from the first detection circuit 6, which is the detection circuit 6. The switching circuit 12 connects the first ultrasonic oscillator 3 to the drive circuit 4, and then separates the first ultrasonic oscillator 3 from the drive circuit 4 and connects it to the second detection circuit 6B. The processor 7 further outputs waveform information regarding the received waveform of the QTE wave C6a detected by the second detection circuit 6B.

[0154] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be determined with even greater accuracy based on the received waveforms of the TTE wave C3a and the QTE wave C6a output from the processor 7. Furthermore, the type of liquid can be determined based on the time difference and amplitude change amount of the received waveforms of the TTE wave C3a and the QTE wave C6a.

[0155] Fifth Embodiment A liquid detection system 1 according to a fifth embodiment will be described with reference to FIG.

[0156] (1) Configuration The liquid detection system 1 according to the fifth embodiment is a device that combines the liquid detection systems 1 according to the first and third embodiments. That is, like the liquid detection system 1 according to the fourth embodiment, the liquid detection system 1 according to the fifth embodiment can also determine the presence or absence of liquid in the pipe 21 based on the received waveforms of the TTE and QTE waves of the ultrasonic waves emitted by the first ultrasonic oscillator 3. In the following description, the second ultrasonic oscillator 16 of the third embodiment will be referred to as the third ultrasonic oscillator 16. In addition, in the following description, the detection circuit 6 will be referred to as the first detection circuit 6, and the detection circuit 6C will be referred to as the second detection circuit 6C.

[0157] 17 , the liquid detection system 1 according to the fifth embodiment is the liquid detection system 1 according to the first embodiment, and further includes the third ultrasonic vibrator 16, the switching circuit 17, the damping circuit 11, and the second detection circuit 6C of the third embodiment. That is, the liquid detection system 1 according to the fifth embodiment includes the first ultrasonic vibrator 3, the drive circuit 4, the second ultrasonic vibrator 5, the first detection circuit 6, the processor 7, the damping circuit 11, the third ultrasonic vibrator 16, the second detection circuit 6C, and the switching circuit 17.

[0158] The first ultrasonic vibrator 3, the drive circuit 4, the second ultrasonic vibrator 5, the first detection circuit 6, and the processor 7 are configured in the same manner as in the first embodiment, and therefore detailed descriptions thereof will be omitted. Also, the damping circuit 11, the switching circuit 17, the third ultrasonic vibrator 16, and the second detection circuit 6C are configured in the same manner as in the third embodiment, and therefore detailed descriptions thereof will be omitted.

[0159] The switching circuit 17 of the fifth embodiment selectively switches the connection partner of the first ultrasonic transducer 3 between the drive circuit 4 and the damping circuit 11. The switching circuit 17 switches the connection partner of the first ultrasonic transducer 3 under the control of the processor 7. Note that the switching of the switching circuit 17 may be performed manually.

[0160] (2) Operation The operation of the liquid detection system 1 according to the fifth embodiment will be described with reference to FIG.

[0161] The switching circuit 17 switches the connection partner of the first ultrasonic transducer 3 between the drive circuit 4 and the damping circuit 11, in that order. More specifically, the switching circuit 17 first connects the first ultrasonic transducer 3 to the drive circuit 4. With this connection, a drive signal from the drive circuit 4 is input to the first ultrasonic transducer 3, causing the first ultrasonic transducer 3 to emit ultrasonic waves. The oscillated ultrasonic waves propagate through the metal portion 21b and the hollow portion 21c of the piping 21. The oscillated ultrasonic waves then propagate as pipe wall propagating waves C1a, submerged direct propagating waves C2a, and TTE waves C3a (see FIG. 2) and are received by the second ultrasonic transducer 5. The oscillated ultrasonic waves also propagate as pipe wall double-circumferential propagating waves C4Ba, DTE waves C5a, and QTE waves C6a (see FIG. 15) and are received by the third ultrasonic transducer 16.

[0162] Then, the switching circuit 17 separates the first ultrasonic transducer 3 from the drive circuit 4 and connects it to the damping circuit 11. This connection allows the damping circuit 11 to suppress reverberation after the oscillation of ultrasonic waves in the first ultrasonic transducer 3. This makes it possible to suppress the influence of reverberation after the oscillation of ultrasonic waves in the first ultrasonic transducer 3 on the reception of ultrasonic waves by the third ultrasonic transducer 16.

[0163] The second ultrasonic transducer 5 receives the tube wall propagation wave C1a, the submerged direct propagation wave C2a, and the TTE wave C3a of the ultrasonic waves emitted by the first ultrasonic transducer 3. The first detection circuit 6 detects the received waveforms of the ultrasonic waves received by the second ultrasonic transducer 5. The third ultrasonic transducer 16 receives the tube wall double-circuit propagation wave C4Ba, the DTE wave C5a, and the QTE wave C6a of the ultrasonic waves emitted by the first ultrasonic transducer 3. The second detection circuit 6C detects the received waveforms of the ultrasonic waves (the tube wall double-circuit propagation wave C4Ba, the DTE wave C5a, and the QTE wave C6a) received by the third ultrasonic transducer 16.

[0164] The processor 7 then outputs the detection results of the first detection circuit 6 and the second detection circuit 6B to the output unit 7a. The user determines whether or not there is liquid in the pipe 21 based on the detection results of the first detection circuit 6 and the second detection circuit 6C output to the output unit 7a. For example, if at least one of the TTE wave C3a and the QTE wave C6a is detected, it is determined that there is liquid in the pipe 21, and if neither the TTE wave C3a nor the QTE wave C6a is detected, it is determined that there is no liquid in the pipe 21. Note that it may also be determined that there is liquid in the pipe 21 if both the TTE wave C3a and the QTE wave C6a are detected, and that there is no liquid in the pipe 21 if neither the TTE wave C3a nor the QTE wave C6a are detected, or if only one of the TTE wave C3a and the QTE wave C6a is detected.

[0165] Furthermore, if it is determined that there is liquid in the pipe 21, the user may further specify the type of liquid determined based on the TTE wave and QTE wave.

[0166] (3) Effects The liquid detection system 1 according to embodiment 5 further includes a third ultrasonic oscillator 16 and a second detection circuit 6C in the liquid detection system 1 according to embodiment 1. The third ultrasonic oscillator 16 is attached to the periphery of the first ultrasonic oscillator 3 in the piping 21. The second detection circuit 6C detects the received waveform of the QTE wave C6a of the ultrasonic waves received by the third ultrasonic oscillator 16. The second detection circuit 6C is different from the first detection circuit 6, which is the detection circuit 6. The processor 7 further outputs waveform information regarding the received waveform of the QTE wave C6a detected by the second detection circuit 6C.

[0167] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be determined with even greater accuracy based on the received waveforms of the TTE wave C3a and the QTE wave C6a output from the processor 7. Furthermore, the type of liquid can be determined based on the time difference and amplitude change amount of the received waveforms of the TTE wave C3a and the QTE wave C6a.

[0168] The first to fifth embodiments and their modifications may be combined and implemented.

[0169] (Aspects) The present specification discloses the following aspects.

[0170] A liquid detection system (1) of a first aspect includes a first ultrasonic transducer (3), a drive circuit (4), a second ultrasonic transducer (5), a detection circuit (6), and an output unit (7a). The first ultrasonic transducer (3) is attached to a metal pipe (21) to be measured. The drive circuit (4) causes the first ultrasonic transducer (3) to emit ultrasonic waves. The second ultrasonic transducer (5) is attached to the pipe (21) on the opposite side from the first ultrasonic transducer (3) and receives ultrasonic TTE waves (C3a) emitted from the first ultrasonic transducer (3). The detection circuit (6) detects the received waveform of the TTE waves (C3a) received by the second ultrasonic transducer (5). The output unit (7a) outputs waveform information related to the received waveform of the TTE waves (C3a) detected by the detection circuit (6).

[0171] According to this configuration, the presence or absence of liquid in the metal pipe (21) can be determined with high accuracy based on the received waveform of the TTE wave (C3a).

[0172] A liquid detection system (1) of a second aspect includes a first ultrasonic transducer (15), a drive circuit (4), a second ultrasonic transducer (16), a detection circuit (6C), and an output unit (7a). The first ultrasonic transducer (15) is attached to a metal pipe (21) that is the measurement target. The drive circuit (4) causes the first ultrasonic transducer (15) to emit ultrasonic waves. The second ultrasonic transducer (16) is attached to the periphery of the first ultrasonic transducer (15) in the pipe (21) and receives an ultrasonic QTE wave (C6a) emitted from the first ultrasonic transducer (15). The detection circuit (6Ca) detects the received waveform of the ultrasonic QTE wave (C6a) received by the second ultrasonic transducer (5). The output unit (7a) outputs waveform information related to the received waveform of the QTE wave (C6a) detected by the detection circuit (6C).

[0173] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be accurately determined based on the received waveform of the QTE wave C6a. Furthermore, since the ultrasonic transducers 15, 16 do not switch between emitting and receiving ultrasonic waves, the processing load can be reduced.

[0174] The liquid detection system (1) of the third aspect is the second aspect, further comprising a damping circuit (11). The damping circuit (11) suppresses reverberation after the ultrasonic wave is generated in the first ultrasonic transducer (15).

[0175] According to this configuration, the damping circuit (11) can prevent reverberation after the ultrasonic wave is generated in the first ultrasonic transducer (15) from being mixed into the received wave of the second ultrasonic transducer (16), thereby improving the detection accuracy of the QTE wave (C6a) by the detection circuit (6C).

[0176] In the liquid detection system (1) of the fourth aspect, in any one of the first to third aspects, at least one of the first ultrasonic vibrator (3; 15) and the second ultrasonic vibrator (5; 16) is attached to the outer surface (21a) of the pipe (21).

[0177] According to this configuration, at least one of the first ultrasonic vibrator (3; 15) and the second ultrasonic vibrator (5; 16) can be attached to the pipe (21) without invasively inserting the first ultrasonic vibrator (3; 15) and the second ultrasonic vibrator (5; 16). Also, the degree of freedom in the location of attachment of at least one of the first ultrasonic vibrator (3; 15) and the second ultrasonic vibrator (5; 16) can be improved.

[0178] The liquid detection system (1) of the fifth aspect is the fourth aspect, further comprising a spacer (30, 31). The spacer (30, 31) is disposed between the first ultrasonic transducer (3; 15) or the second ultrasonic transducer (5; 16) and the convex curved surface portion of the outer surface (21a) of the pipe (21). The spacer (30, 31) has a concave curved surface portion (30a, 31a) and a flat surface portion (30b, 31b). The concave curved surface portion (30a, 31a) fits into the convex curved surface portion of the pipe (21). The flat surface portion (30b, 31b) is where the first ultrasonic transducer (3; 15) or the second ultrasonic transducer (5; 16) is disposed.

[0179] According to this configuration, the spacer (30, 31) can fill the gap between the first ultrasonic vibrator (3; 15) or the second ultrasonic vibrator (5; 16) and the convex curved portion of the outer surface (21 a) of the pipe (21), thereby facilitating the propagation of ultrasonic waves between the first ultrasonic vibrator (3; 15) or the second ultrasonic vibrator (5; 16) and the pipe (21), thereby improving the detection accuracy of the detection circuit (6; 6C).

[0180] A liquid detection system (1) according to a sixth aspect includes an ultrasonic transducer (10), a drive circuit (4), a detection circuit (6B), a switching circuit (12), and an output unit (7a). The ultrasonic transducer (10) is attached to a metal pipe (21) to be measured. The drive circuit (4) is connected to the ultrasonic transducer (10) and causes the ultrasonic transducer (10) to emit ultrasonic waves. The detection circuit (6B) is connected to the ultrasonic transducer (10) and detects the received waveform of an ultrasonic QTE wave (C6a) received by the ultrasonic transducer (10). The switching circuit (12) connects the ultrasonic transducer (10) to the drive circuit (4) and then separates the ultrasonic transducer (10) from the drive circuit (4) and connects it to the detection circuit (6B). The output unit (7a) outputs waveform information related to the received waveform of the QTE wave (C6a) detected by the detection circuit (6B).

[0181] According to this configuration, based on the received waveform of the QTE wave (C6a), it is possible to accurately determine the presence or absence of liquid in the metal pipe (21). Furthermore, since the ultrasonic wave is emitted and received by a single ultrasonic vibrator (10), the work of attaching the ultrasonic vibrator (10) to the pipe (21) can be reduced, and costs can be reduced.

[0182] The liquid detection system (1) of the seventh aspect is the sixth aspect, further comprising a damping circuit (11). The damping circuit (11) is connected to the ultrasonic transducer (10) to suppress reverberation after ultrasonic oscillation in the ultrasonic transducer (10). The switching circuit (12) switches the connection of the ultrasonic transducer (10) between the drive circuit (4), the damping circuit (11), and the detection circuit (6B), in that order.

[0183] According to this configuration, the damping circuit (11) can prevent reverberation after the ultrasonic wave is generated in the ultrasonic transducer (10) from being mixed into the received wave of the ultrasonic transducer (10), thereby improving the detection accuracy of the QTE wave (C6a) by the detection circuit (6B).

[0184] In the liquid detection system (1) of the eighth aspect, in the sixth or seventh aspect, the ultrasonic vibrator (10) is attached to the outer surface (21a) of the pipe (21).

[0185] According to this configuration, the ultrasonic vibrator (10) can be attached to the pipe (21) without invasively inserting the pipe (21). Also, the ultrasonic vibrator (10) can be installed at a more flexible location.

[0186] The liquid detection system (1) of a ninth aspect is the eighth aspect, further comprising a spacer. The spacer is disposed between the ultrasonic transducer (10) and the convex curved portion of the outer surface (21a) of the pipe (21). The spacer has a concave curved portion and a flat portion. The concave curved portion fits into the convex curved portion of the pipe (21). The ultrasonic transducer is disposed on the flat portion.

[0187] According to this configuration, the spacer can fill the gap between the ultrasonic vibrator (10) and the convex curved portion of the outer surface (21 a) of the pipe (21), which facilitates the propagation of ultrasonic waves between the ultrasonic vibrator (10) and the pipe (21), thereby improving the detection accuracy of the detection circuit (6B).

[0188] The liquid detection system (1) of the tenth aspect is the same as that of the first aspect, but further includes a third ultrasonic oscillator (16) and a second detection circuit (6C). The third ultrasonic oscillator (16) is attached to the piping (21) around the first ultrasonic oscillator (3). The second detection circuit (6C) detects the received waveform of the ultrasonic QTE wave (C6a) received by the third ultrasonic oscillator (16). The second detection circuit (6C) is different from the first detection circuit (6), which is the detection circuit (6). The output unit (7a) further outputs waveform information regarding the received waveform of the QTE wave (C6a) detected by the second detection circuit (6C).

[0189] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be determined with greater accuracy based on the received waveforms of the TTE wave (C3a) and the QTE wave (C6a).Furthermore, the type of liquid can be determined based on the time difference and amplitude change of the received waveforms of the TTE wave (C3a) and the QTE wave (C6a).

[0190] The liquid detection system (1) of the eleventh aspect is the same as that of the first aspect, but further includes a second detection circuit (6B) and a switching circuit (12). The second detection circuit (6B) detects the received waveform of the ultrasonic QTE wave (C6a) received by the first ultrasonic transducer (3). The second detection circuit (6B) is different from the first detection circuit (6), which is the detection circuit (6). The switching circuit (12) connects the first ultrasonic transducer (3) to the drive circuit (4), and then separates the first ultrasonic transducer (3) from the drive circuit (4) and connects it to the second detection circuit (6B). The output unit (7a) further outputs waveform information regarding the received waveform of the QTE wave (C6a) detected by the second detection circuit (6B).

[0191] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be determined with greater accuracy based on the received waveforms of the TTE wave (C3a) and the QTE wave (C6a).Furthermore, the type of liquid can be determined based on the time difference and amplitude change of the received waveforms of the TTE wave (C3a) and the QTE wave (C6a).

[0192] A liquid detection method according to a twelfth aspect includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a first ultrasonic transducer (3) is attached to a metal pipe (21) to be measured. In the second step, ultrasonic waves are emitted from the first ultrasonic transducer (3) by a drive circuit (4). In the third step, a second ultrasonic transducer (5) is attached to the pipe (21) on the opposite side from the first ultrasonic transducer (3), and the second ultrasonic transducer (5) receives ultrasonic TTE waves (C3a) emitted from the first ultrasonic transducer (3). In the fourth step, the received waveform of the ultrasonic TTE waves (C3a) received by the second ultrasonic transducer (5) is detected by a detection circuit (6). In the fifth step, waveform information relating to the received waveform of the TTE waves (C3a) detected by the detection circuit (6) is output from an output unit (7a).

[0193] According to this configuration, the presence or absence of liquid in the metal pipe (21) can be determined with high accuracy based on the received waveform of the TTE wave (C3a).

[0194] A liquid detection method according to a thirteenth aspect includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, a first ultrasonic transducer (15) is attached to a metal pipe (21) to be measured. In the second step, ultrasonic waves are emitted from the first ultrasonic transducer (15) by a drive circuit (4). In the third step, a second ultrasonic transducer (16) is attached to the periphery of the first ultrasonic transducer (15) in the pipe (21), and the second ultrasonic transducer (16) receives an ultrasonic QTE wave (C6a) emitted from the first ultrasonic transducer (15). In the fourth step, a detection circuit (6C) detects the received waveform of the QTE wave (C6a) received by the second ultrasonic transducer (16). In the fifth step, waveform information relating to the received waveform of the QTE wave (C6a) detected by the detection circuit (6C) is output from an output unit (7a).

[0195] According to this configuration, the presence or absence of liquid in the metal pipe 21 can be accurately determined based on the received waveform of the QTE wave C6a. Furthermore, since the ultrasonic transducers 15, 16 do not switch between emitting and receiving ultrasonic waves, the processing load can be reduced.

[0196] A liquid detection method according to a fourteenth aspect includes a first step, a second step, a third step, a fourth step, and a fifth step. In the first step, an ultrasonic transducer (10) is attached to a metal pipe (21) to be measured. In the second step, an ultrasonic wave is generated from the ultrasonic transducer (10) by a drive circuit (4). In the third step, a received waveform of the ultrasonic wave received by the ultrasonic transducer (10) is detected by a detection circuit (6B). In the fourth step, the ultrasonic transducer (10) is connected to the drive circuit (4), and then the ultrasonic transducer (10) is disconnected from the drive circuit (4) and connected to a detection circuit (6B). In the fifth step, waveform information regarding the received waveform of the QTE wave (C6a) detected by the detection circuit (6B) is output from an output unit (7a).

[0197] According to this configuration, based on the received waveform of the QTE wave (C6a), it is possible to accurately determine the presence or absence of liquid in the metal pipe (21). Furthermore, since the ultrasonic wave is emitted and received by a single ultrasonic vibrator (10), the work of attaching the ultrasonic vibrator (10) to the pipe (21) can be reduced, and costs can be reduced.

[0198] DESCRIPTION OF SYMBOLS 1 Liquid detection system 2, 21 Piping 2a Outer surface 3 First ultrasonic vibrator 3a Contact surface 3s Top surface 4 Drive circuit 5 Second ultrasonic vibrator 5a Contact surface 5s Top surface 6 Detection circuit (first detection circuit) 6B Detection circuit (second detection circuit) 6C Detection circuit (second detection circuit) 7 Processor 7a Output unit 10 Ultrasonic vibrator 10a Contact surface 11 Damping circuit 12 Switching circuit 12a Common terminal 12b to 12d Selection terminal 15 Ultrasonic vibrator (first ultrasonic vibrator) 16 Ultrasonic vibrator (second ultrasonic vibrator, third ultrasonic vibrator) 17 Switching circuit 17a Common terminal 17b, 17c Selection terminal 21a Outer surface 21b Metal part 21c Cavity part 21d, 21e Flat part 21f, 21g Storage portion 30, 31 Spacer 30a, 31a Concave curved surface portion 30b, 31b Plane portion 40 Fastener 41 Main body portion 41a Contact surface 41b Screw hole 42 Pressing portion 42a Contact surface 42b Back surface 43 Threaded portion 44 Handle portion c1 Speed ​​of sound C1a Pipe wall propagating wave C2a Directly propagating wave in liquid C3a TTE wave C4Aa Pipe wall single cycle propagating wave C4Ba Pipe wall propagating wave twice C5a DTE wave C6a QTE wave D1 Inner diameter

Claims

1. A liquid detection system comprising: a first ultrasonic vibrator attached to a metal pipe to be measured; a drive circuit that causes the first ultrasonic vibrator to emit ultrasonic waves; a second ultrasonic vibrator attached to the pipe on the opposite side from the first ultrasonic vibrator and that receives the ultrasonic TTE waves emitted from the first ultrasonic vibrator; a detection circuit that detects the received waveform of the TTE waves received by the second ultrasonic vibrator; and an output unit that outputs waveform information regarding the received waveform of the TTE wave detected by the detection circuit.

2. A liquid detection system comprising: a first ultrasonic vibrator attached to a metal pipe to be measured; a drive circuit that causes the first ultrasonic vibrator to emit ultrasonic waves; a second ultrasonic vibrator attached to the pipe around the first ultrasonic vibrator and receiving the ultrasonic QTE waves emitted from the first ultrasonic vibrator; a detection circuit that detects the received waveform of the ultrasonic QTE waves received by the second ultrasonic vibrator; and an output unit that outputs waveform information regarding the received waveform of the QTE wave detected by the detection circuit.

3. The liquid detection system according to claim 2, further comprising a damping circuit that suppresses reverberation after the ultrasonic waves are oscillated in the first ultrasonic vibrator.

4. A liquid detection system according to any one of claims 1 to 3, wherein at least one of the first ultrasonic vibrator and the second ultrasonic vibrator is attached to the outer surface of the pipe.

5. A liquid detection system as described in claim 4, further comprising a spacer arranged between the first ultrasonic vibrator or the second ultrasonic vibrator and the convex curved portion of the outer surface of the piping, the spacer having a concave curved portion that fits into the convex curved portion of the piping, and a flat portion on which the first ultrasonic vibrator or the second ultrasonic vibrator is arranged.

6. A liquid detection system comprising: an ultrasonic vibrator attached to a metal pipe to be measured; a drive circuit connected to the ultrasonic vibrator and causing the ultrasonic vibrator to emit ultrasonic waves; a detection circuit connected to the ultrasonic vibrator and detecting the received waveform of the QTE wave of the ultrasonic wave received by the ultrasonic vibrator; a switching circuit that connects the ultrasonic vibrator to the drive circuit, and then separates the ultrasonic vibrator from the drive circuit and connects it to the detection circuit; and an output unit that outputs waveform information regarding the received waveform of the QTE wave detected by the detection circuit.

7. The liquid detection system according to claim 6, further comprising a damping circuit connected to the ultrasonic vibrator to suppress reverberation after the ultrasonic vibration is generated in the ultrasonic vibrator, and the switching circuit switches the connection of the ultrasonic vibrator between the drive circuit, the damping circuit, and the detection circuit in that order.

8. The liquid detection system according to claim 6 or 7, wherein the ultrasonic vibrator is attached to the outer surface of the pipe.

9. A liquid detection system as described in claim 8, further comprising a spacer disposed between the ultrasonic vibrator and the convex curved portion of the outer surface of the piping, the spacer having a concave curved portion that fits into the convex curved portion of the piping, and a flat portion on which the ultrasonic vibrator is disposed.

10. The liquid detection system of claim 1, further comprising: a third ultrasonic vibrator attached around the first ultrasonic vibrator in the piping; and a second detection circuit different from the first detection circuit, which is the detection circuit, that detects the received waveform of the ultrasonic QTE wave received by the third ultrasonic vibrator, wherein the output unit further outputs waveform information regarding the received waveform of the QTE wave detected by the second detection circuit.

11. A liquid detection system as described in claim 1, further comprising: a second detection circuit different from the first detection circuit, which is the detection circuit, that detects the received waveform of the ultrasonic QTE wave received by the first ultrasonic vibrator; and a switching circuit that connects the first ultrasonic vibrator to the drive circuit, and then separates the first ultrasonic vibrator from the drive circuit and connects it to the second detection circuit, wherein the output unit further outputs waveform information regarding the received waveform of the QTE wave detected by the second detection circuit.

12. A liquid detection method comprising: a first step of attaching a first ultrasonic vibrator to a metal pipe to be measured; a second step of causing the first ultrasonic vibrator to emit ultrasonic waves using a drive circuit; a third step of attaching a second ultrasonic vibrator to the pipe on the opposite side to the first ultrasonic vibrator and receiving the ultrasonic TTE wave emitted from the first ultrasonic vibrator using the second ultrasonic vibrator; a fourth step of detecting, using a detection circuit, the received waveform of the TTE wave of the ultrasonic wave received by the second ultrasonic vibrator; and a fifth step of outputting, from an output unit, waveform information relating to the received waveform of the TTE wave detected by the detection circuit.

13. A liquid detection method comprising: a first step of attaching a first ultrasonic vibrator to a metal pipe to be measured; a second step of causing the first ultrasonic vibrator to emit ultrasonic waves using a drive circuit; a third step of attaching a second ultrasonic vibrator to the periphery of the first ultrasonic vibrator in the pipe and receiving the ultrasonic QTE waves emitted from the first ultrasonic vibrator using the second ultrasonic vibrator; a fourth step of detecting the received waveform of the QTE waves received by the second ultrasonic vibrator using a detection circuit; and a fifth step of outputting waveform information relating to the received waveform of the QTE waves detected by the detection circuit from an output unit.

14. A liquid detection method comprising: a first step of attaching an ultrasonic vibrator to a metal pipe to be measured; a second step of causing the ultrasonic vibrator to emit ultrasonic waves using a drive circuit; a third step of detecting the received waveform of the ultrasonic waves received by the ultrasonic vibrator using a detection circuit; a fourth step of connecting the ultrasonic vibrator to the drive circuit, and then separating the ultrasonic vibrator from the drive circuit and connecting it to the detection circuit; and a fifth step of outputting waveform information relating to the received waveform of the QTE wave detected by the detection circuit from an output unit.

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