JPH04276548A - Ultrasonic probe and ultrasonic diagnosis method - Google Patents

Abstract

PURPOSE:To input ultrasonic waves having plural kinds of frequencies and to make it possible to diagnose objects from the small size to the large size accurately by laminating a plurality of piezoelectric transducers in the orthogonally intersecting direction with respect to the attaching surface of a body to be measured in the same container. CONSTITUTION:When a switch 23a of a signal switching circuit 23 is thrown to the side of a signal line 30b, the pulse signals from a pulse signal generating circuit 7 are applied on electrodes 28a and 28b of a piezoelectric transducer 26. As a result, an ultrasonic wave 21 having the frequency f1 is sent into the direction of the thickness of a body to be measured 4. When the switch 23a is thrown to the side of a signal line 30c, the pulse signal is applied across electrodes 28a and 29b of the piezoelectric transducers 26 and 27 through the signal lines 30c and 30a. At this time, the piezoelectric transducers 26 and 27 are operated as one synthesized piezoelectric transducer, and an ultrasonic wave 21 having the frequency f2 (= about f1/2) is sent out to the body to be measured 4. Therefore, a fine flaw in the shallow surface layer part of the body to be measured 4 can be detected with the high frequency f1, and a large flaw in the deep inner material can be detected with the low frequency f2.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe in which a plurality of stacked transducers are assembled in the same container, and an ultrasonic diagnostic method using this ultrasonic probe.

0002

2. Description of the Related Art Ultrasonic flaw detection has been put into practical use as one of the flaw detection techniques for detecting defects present in objects to be measured, such as steel plates. FIG. 9 is a diagram showing an ultrasonic flaw detection device using an ultrasonic probe.

In the ultrasonic probe 1, a single transducer 3 for transmitting and receiving ultrasonic waves is placed in a container 2 filled with a damper material on a mounting surface 4a of a measuring object 4 such as a steel plate. are arranged in parallel. Further, the vibrator 3 is connected to a terminal 6 provided on the container 2 through a signal line 5. When a pulse signal is applied to the transducer 3 from the pulse generating circuit 7 in the external flaw detector via the signal line 5, the ultrasonic wave 8 is sent from the transducer 3 in the thickness direction (vertical direction) of the object to be measured 4. be done.

[0004] Ultrasonic waves 8 propagating vertically within the object to be measured 4 are reflected by, for example, the opposite surface (bottom surface) of the object to be measured 4 and are incident on the same transducer 3 . The reflected wave (echo) incident on the vibrator 3 is converted into an electrical signal and received as a received signal by the receiving circuit 9 of the flaw detector via the signal line 5. The receiving circuit 9 detects the received signal and sends it to the cathode ray tube 10. Therefore, the received signal detected by the receiving circuit 9 includes a transmitted pulse wave T as shown on the cathode ray tube 10.
and a reflected wave B at the bottom surface.

[0005] Here, if a defect 11 exists inside the object to be measured 4, the ultrasonic wave 8 is reflected by this defect 11.
A defective wave F is generated between the transmitted pulse wave T and the bottom reflected wave B due to the defect. Therefore, it is possible to specify the defect occurrence position (occurrence depth) and the scale indicated by the waveform height.

[0006]

However, the ultrasonic flaw detection apparatus shown in FIG. 9 still has the following problems.

That is, when a pulse signal is applied to the vibrator 3 of the ultrasonic probe 1, the vibrator 3 starts to vibrate (resonate) by expanding and contracting in accordance with the thickness t. Then, it vibrates several times, decays, and stops. Therefore, the frequency f of the ultrasonic waves 8 that enter the object to be measured 4 from the ultrasonic probe 1 is uniquely determined by the thickness t of the transducer 3. This means that only the ultrasonic waves 8 having a single preset frequency f can be incident on the object to be measured 4 using one ultrasonic probe 1 .

On the other hand, the attenuation characteristics of the ultrasonic waves 8 within the object to be measured 4 vary greatly depending on the frequency f of the ultrasonic waves 8. That is, when the frequency f is high, it is relatively easy to attenuate, and when the frequency f is low, it is relatively difficult to attenuate. Furthermore, fine defects are relatively easy to detect using ultrasonic waves with a high frequency f, and there is a concern that the detection ability may deteriorate at low frequencies.

Furthermore, the defect 1 can be removed from the mounting surface 4a of the object to be measured 4.
FIG. 10 shows a DGS diagram showing the relationship between the distance x to the position where 1 exists and the defect echo height represented by the ratio (F/B) of the defect wave F to the bottom reflected wave B. As shown in the figure, as the distance x to the defect 11 increases, the detection sensitivity indicated by the echo height decreases. Further, the parameter G in the figure is the ratio between the size (scale) d of the defect 11 and the outer diameter D of the vibrator 3 (G=d/D). In this way, the damping characteristics vary greatly depending on the dimensions of the vibrator 3.

[0010] Thus, the ability to detect defects at any position within the object to be measured 4 is approximately determined by the frequency f of the ultrasonic wave 8 and the dimensions of the vibrator 3. Conversely, this means that the object to be measured 4
Therefore, it is not possible to arbitrarily set the defect detection sensitivity distribution for each position within the area.

Therefore, in general, when testing the object 4 to be measured, ultrasonic waves 8 are used to detect the thickness, crystal grain size, etc. of the object 4 to be measured.
Considering the factors that affect the transmittance of the ultrasonic wave 8, a frequency f is selected that allows the ultrasonic wave 8 to pass through and be reflected, and at which a sufficient S/N ratio can be obtained.

As a result, the desired detection ability (sensitivity) is obtained for the internal part of the object to be measured 4, but the detection ability (sensitivity) is too high for the surface layer, and unnecessary detection is achieved. There is a problem that even flaws are detected. Conversely, the superficial layer can achieve the desired detection ability (sensitivity), but the internal layer can achieve the detection ability (sensitivity).
There is a problem of insufficient sensitivity.

Conventionally, in order to eliminate such inconveniences, a method has been implemented in which a plurality of ultrasonic probes with different frequencies are prepared and the same location on the object to be measured 4 is inspected twice. However, since it is necessary to combine the separately obtained received signals and perform signal processing, an advanced and complex system is required that includes correction processing for the installation position of the ultrasound probe, etc. Furthermore, it is necessary to measure the same location twice using different ultrasonic probes, which reduces the efficiency of flaw detection work.

The present invention has been made in view of the above circumstances, and by stacking a plurality of vibrators in the same container, it is possible to excite each vibrator alone or by connecting each vibrator. Ultrasonic probes and ultrasonic probes that can inject ultrasonic waves of multiple types of frequencies into the object to be measured, achieve the desired detection sensitivity from short to long distances, and accurately diagnose small to large objects. The purpose is to provide a method for sonic diagnosis.

[0015]

[Means for Solving the Problems] In order to solve the above problems, the ultrasonic probe of the present invention is incorporated in the same container,
A plurality of transducers are stacked in a direction perpendicular to the mounting surface of the object to be measured, electrodes are attached to both ends of each of the stacked transducers, and a plurality of transducers are used to guide signals sent and received from each electrode to the outside of the container. It is equipped with a signal line.

[0016] Furthermore, according to the ultrasonic diagnostic method of the present invention,
Multiple transducers stacked in a direction perpendicular to the mounting surface of the object to be measured are built into the same container, and signal lines are led out from the container from electrodes attached to both ends of each transducer. By simultaneously or alternately selecting a combination of a pair of signal lines from among a plurality of signal lines and applying a pulse signal between the selected pair of signal lines, a plurality of different frequencies can be transmitted into the body under test. Ultrasonic diagnosis is performed by injecting ultrasonic waves that have a

[0017]

[Operation] According to the ultrasonic probe and ultrasonic diagnostic method constructed as described above, a plurality of transducers are stacked in one container. Signal lines are led out of the container from electrodes attached to both sides of each vibrator.

Therefore, the signal line connected to the electrode on the bottom surface of the vibrator located at the lowest end of the plurality of stacked probes and the signal wire connected to the electrode on the top surface of the vibrator located at the top end. When a pulse signal is applied between the wire and the wire, the plurality of stacked vibrators are regarded as one vibrator and vibrate. The frequency of vibration in this case is determined by the sum of the thicknesses of all the stacked vibrators.

Conversely, when a pulse signal is applied between the signal line connected to the electrode on the bottom surface of the vibrator located at the lowest end and the signal line connected to the electrode on the top surface of the same vibrator, Only the oscillator vibrates. The frequency of vibration in this case is determined by the thickness of the lowest vibrator.

[0020] In this way, by appropriately switching between the pair of signal lines to which pulse signals are applied, ultrasonic waves having multiple types of frequencies can be made to enter the object to be measured using one ultrasonic probe. is possible. Therefore, it is possible to use different ultrasonic frequencies depending on the distance from the mounting surface of the object to be measured, and arbitrary detection ability (sensitivity) can be set.

[0021]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 is a schematic diagram showing the configuration of an ultrasonic flaw detection apparatus to which an ultrasonic probe and an ultrasonic diagnostic method are applied. The same parts as in FIG. 9 are given the same reference numerals. Therefore, detailed explanation of the overlapping parts will be omitted.

This ultrasonic flaw detection apparatus is broadly divided into an ultrasonic probe 22 that transmits and receives ultrasonic waves 21 to and from an object 4 to be measured such as a steel plate, and a probe for each transducer of this ultrasonic probe 22. It is comprised of a signal switching circuit 23 that switches signals, and a flaw detector 24 that sends pulse signals to the ultrasonic probe 22 via the signal switching circuit 23 and processes received signals.

In the ultrasonic probe 22, two transducers 2 having the same configuration are placed in a container 25 filled with damper material.
6 and 27 are stacked in a direction perpendicular to the mounting surface 4a of the object to be measured 4. Electrodes 28a, 28b, 29a, and 29b are attached to the upper and lower surfaces of each vibrator 26 and 27, respectively. Note that the actual boundary surface is composed of the electrodes of each vibrator. Each electrode 28a, 28b (29a), 29b
Signal lines 30a, 30b, and 30c are connected to the signal switching circuit 23 via terminals 31 attached to the container 25.

The signal switching circuit 23, as shown in FIG.
It has a function of selecting a pair of signal lines from the three signal lines 30a, 30b, and 30c. The signal line 30a serving as a common ground is directly connected to the (-) side terminal of the flaw detector 24, and the signal lines 30b and 30c are connected to the (+) side terminal of the flaw detector 24 via the changeover switch 23a.

The changeover switch 23a may be, for example, a snap switch, a mercury relay, a relay using a normal coil, or an I
It is composed of electronic switching circuits such as C and SCR. This changeover switch 23a is controlled by a synchronization circuit 32 within the flaw detector 24.

The flaw detector 24 also includes a pulse generating circuit 7,
Receiving circuit 9, cathode ray tube 10, and signal switching circuit 23
It is composed of a synchronization circuit 32 that synchronizes the switching operation of the display with the content displayed on the cathode ray tube 10.

In the ultrasonic flaw detector configured as described above, (1) With the changeover switch 23a of the signal changeover circuit 23 turned on to the signal line 30b side, the pulse signal is output from the pulse generation circuit 7 in the flaw detector 24. When output, this pulse signal passes through the signal switching circuit 23 to the signal line 30a and the signal line 3.
0b, the electrodes 28a, 28 of the lower vibrator 26
b.

As a result, the lower vibrator 26 vibrates at a frequency f1 uniquely determined by the thickness of this vibrator 26,
Ultrasonic waves 21 having a frequency f1 are transmitted in the thickness direction (vertical direction) of the object 4 to be measured. The ultrasonic wave 21 propagated vertically within the object to be measured 4 is e.g.
, and enters the same vibrator 26 . Vibrator 2
The reflected wave (echo) incident on 6 is converted into an electrical signal and sent to signal lines 30a, 30b and signal circuit 2 as a received signal.
3 and is received by the receiving circuit 9 of the flaw detector 24. The receiving circuit 9 detects the received signal and sends it to the cathode ray tube 10. Therefore, the received signal detected by the receiving circuit 9 has the following:
As shown in the cathode ray tube 10, a transmitted pulse wave T and a reflected wave B from the bottom surface are included.

[0030] Here, if a defect 11 exists inside the object to be measured 4, the ultrasonic wave 21 is reflected by this defect 11, so that there is a difference between the transmitted pulse wave T and the bottom reflected wave B due to the defect 11. A defective wave F is generated. Therefore, it is possible to specify the defect occurrence position (occurrence depth) and the scale indicated by the waveform height (echo height).

(2) Next, with the changeover switch 23a of the signal changeover circuit 23 turned on to the signal line 30c side, when a pulse signal is output from the pulse generation circuit 7 in the flaw detector 24, this pulse signal is activated by the signal changeover circuit. The lower vibrator 26 is connected via the circuit 23 to the signal line 30a and the signal line 30c.
The electrode 28a on the lower surface of the oscillator 27 and the electrode 2 on the upper surface of the upper vibrator 27
9b.

In this case, since the vibrators 26 and 27 are laminated with the thin electrode 28b (29a) interposed therebetween, the two vibrators 26 and 27 operate like a combined vibrator. As a result, the transducers 26 and 27 vibrate at a frequency f2 uniquely determined by the equivalent thickness added together, and an ultrasonic wave 21 with a frequency f2 is transmitted in the thickness direction (vertical direction) of the object to be measured 4. be done. As a result, a defect wave F caused by the defect 11 existing in the object to be measured 4 is generated in the cathode ray tube 10, similar to the ultrasonic wave 21 having the frequency f1.

In vibrators formed of the same material and having the same outer diameter, the thicker the vibrator, the lower the frequency it vibrates. Therefore, the two oscillators 26 and 27 were excited (
The frequency f2 of the combination condition 2) is approximately 1/2 of the frequency f1 of the combination condition (1) in which only one vibrator 28 is excited.

Therefore, by controlling the changeover switch 23a of the signal changeover circuit 23 at a constant cycle using the synchronization circuit 32, the shallow surface portion in the thickness direction at the same position on the mounting surface 4a of the object to be measured 4 can be changed to a high frequency f1. By performing flaw detection at f2, fine flaws in the surface layer can be detected, and large flaws can be detected by flaw detection at a low frequency f2 in the deep inner part where concentrated stress is less likely to occur.

Furthermore, since the ultrasonic wave with a low frequency f2 has little decrease in detection sensitivity even at a deep position in the thickness direction, there is no need to electrically amplify the detection sensitivity using an ultrasonic wave with a high frequency f1. The S/N ratio can be maintained high over a wide distance range in the thickness direction. That is, it is possible to accurately detect everything from minute flaws near the surface of the object to be measured 4 to large flaws in the endoplasmic part with the best detection sensitivity.

Furthermore, compared to the case where a plurality of ultrasonic probes with different ultrasonic frequencies are used to detect flaws at the same position on the mounting surface 4a, only one installation positioning operation is required. Eliminates alignment errors between probes,
In addition, flaw detection work efficiency can be greatly improved.

As is well known, the relationship between the thickness t of the vibrator and the vibration frequency f is as follows, where λ is the wavelength, C is the speed of sound,
If K is a constant, λ=C/f and t=λ/2, so the following equation is obtained. f=2K/t Therefore, it is possible to design and manufacture the thickness t of the vibrator from the required frequency f. Next, experimental results using an actual ultrasound probe will be explained.

As the vibrators 26 and 27 in FIG. 1, the outer diameter D=
10mm, thickness t=0.4mm, standard frequency f=5.
2MHz, a resonator made of lead titanate material is used. Also,
The experiment adopted the water immersion method, and the water distance was about 30 mm.

Under the above-mentioned combination condition (1) in which a pulse signal is applied between the signal line 30a and the signal line 30b, the received signal input to the receiving circuit 9 is as shown in FIG. 3(a), and the frequency is f1. =5.17MHz. Further, the detection sensitivity at that time was 64 dB.

Furthermore, under the combination condition (2) in which a pulse signal is applied between the signal line 30a and the signal line 30c, the received signal becomes as shown in FIG. 3(b), and the frequency is f2 = 2.14M.
It is Hz. Further, the detection sensitivity at that time was 51 dB.

In this way, by changing the combination of the transducers 26 and 27 to which pulse signals are applied using the signal switching circuit 23, ultrasonic waves having two types of frequencies f1 and f2 can be obtained using the same ultrasonic probe 22. Flaws can be detected using sound waves 21.

FIG. 4 is a schematic diagram showing an ultrasonic flaw detection apparatus to which an ultrasonic probe and an ultrasonic diagnostic method according to another embodiment of the present invention are applied. The same parts as in the embodiment of FIG. 1 are given the same reference numerals. Therefore, detailed explanation of the overlapping parts will be omitted.

In this embodiment, two types of vibrators 41 and 42 having the same outer diameter and different thicknesses t are stacked with an insulating material 43 interposed between them. Then, each signal line 44 is connected to each electrode 41a, 41b, 42a, 42b attached to the lower surface and upper surface of each vibrator 41, 42, respectively.
a, 44b, 44c, and 44d are input to a signal switching circuit 45 via a terminal 31 attached to the container 25.

FIG. 5 is a circuit diagram of the signal switching circuit 45. This signal switching circuit 45 has two changeover switches 45a and 4.
5b and one switch 45c. Then, in this signal switching circuit 45, the following three combination conditions (3), (4), and (5) are set for each vibrator 41, 42 by a switching command from the synchronous circuit 32 in the flaw detector 24. can be set.

The combination condition (3) is to release the switch 45c and connect the changeover switches 45a and 45b to the signal line 44a.
, 44b side, and the pulse signal is sent to the lower vibrator 41.
Apply only to

The combination condition (4) is to close the switch 45c, turn on the changeover switch 45a to the signal line 44a side, and turn on the changeover switch 45b to the signal line 44d side. Then, a pulse signal is applied to both ends of the stacked vibrators 41 and 42.

The combination condition (5) is to release the switch 45c and connect the changeover switches 45a and 45b to the signal line 44c.
, 44d side, and the pulse signal is sent to the upper vibrator 42.
Apply only to

By stacking the two types of vibrators 41 and 42 with different thicknesses t through the insulating material 43 in this way, it is possible to excite each vibrator 41 and 42 individually and to excite them in combination. (3) to (5) mentioned above
Three types of equivalent thickness shown in can be secured. the result,
Corresponding to each equivalent thickness t, three types of frequencies f3,
f4 and f5 can be realized.

Therefore, compared to the device that can obtain two types of frequencies f1 and f2 shown in FIG.
It is possible to divide it into two regions and assign the best frequency f to each region. Therefore, detection sensitivity adjustment can be performed more finely. Next, experimental results using an actual ultrasound probe will be explained.

As the vibrator 41 in FIG. 4, the outer diameter D=10 m
m, thickness t=0.25mm, standard frequency f=10MHz
, a resonator made of lead titanate material is used. In addition, the vibrator 4
2, outer diameter D = 10 mm, thickness t = 1.0 mm,
A standard frequency f=2 MHz and a vibrator made of lead titanate material are used.

Note that when only one vibrator is excited, the other vibrator on the back side vibrates in response to the normal vibration of the excited vibrator, as shown in FIG. An interference phenomenon occurs due to the vibrator. Therefore, there is a concern that the S/N of the obtained received signal will decrease.

Therefore, in order to prevent such interference phenomenon, as shown in FIG.
A 0.1 μH impedance matching coil 46a is inserted in the signal line 44d, and a 20 μH impedance matching coil 46d is inserted in the signal line 44d.

Under the above-mentioned combination condition (3) in which a pulse signal is applied between the signal line 44a and the signal line 44b, the received signal input to the receiving circuit 9 is as shown in FIG. 7(a), and the frequency is f3. =10.17 MHz. Furthermore, under the combination condition (4) in which a pulse signal is applied between the signal line 44a and the signal line 44d, the received signal is as shown in FIG. 7(b).
Therefore, the frequency is f4 = 1.54 MHz.

Furthermore, under the combination condition (5) in which a pulse signal is applied between the signal line 44c and the signal line 44d, the received signal becomes as shown in FIG. 7(c), and the frequency is f5 = 2.0.
It is MHz.

In this way, by changing the combination of the transducers 41 and 42 to which pulse signals are applied using the signal switching circuit 45, three types of frequencies f3, f4, and f5 can be generated using the same ultrasonic probe 21. Flaw detection can be performed using the ultrasonic waves 21. Note that the present invention is not limited to the embodiments described above.

For the switching timing of the above-mentioned combination conditions (1) to (5) of the vibrators in the signal switching circuits 23 and 45, an alternate excitation method in which the synchronization circuit 32 switches at a constant cycle is adopted. The circuit configurations of the circuits 23 and 45 may be changed to adopt a simultaneous excitation method in which excitation is simultaneously performed under the plurality of combination conditions described above. That is, by selecting the optimal conditions from among various combinations and excitation conditions and performing signal processing, the best S/N in flaw detection processing can be achieved. Also, the specifications of each vibrator stacked inside the container do not need to be the same;
It is possible to arbitrarily combine the outer diameter, material, etc. to obtain the desired frequency.

Furthermore, the material of each vibrator is not limited to lead titanate, but may also be lead zincate. Furthermore, a combination of lead titanate and lead zincate may be used.

Further, in the embodiment, the case where the ultrasonic diagnostic method is applied to an ultrasonic flaw detection device has been described, but it can also be applied to medical diagnosis, material inspection, and structural inspection of composite materials using ultrasonic waves, for example. Of course it is possible.

[0059]

Effects of the Invention As explained above, according to the ultrasonic probe of the present invention, a plurality of transducers are stacked in the same container, and signal lines are routed from the electrodes on both sides of each transducer to the outside of the container. It is derived. Therefore, by selecting the signal line to which the pulse signal is applied, each vibrator can be excited individually or in a connected manner, thereby allowing ultrasonic waves of a plurality of different frequencies to be incident on the object to be measured.

Furthermore, in the ultrasonic diagnostic method, by using the above-mentioned ultrasonic flaw detection probe, the frequency of the ultrasonic waves can be selected, so that it can be applied over a wide range from short distances to long distances on the mounting surface of the object to be measured. The desired detection sensitivity can be set across the range, allowing accurate diagnosis of both small and large objects.

[Brief explanation of the drawing]

FIG. 1 is a schematic configuration diagram of an ultrasonic flaw detection apparatus using an ultrasonic probe and an ultrasonic diagnostic method according to an embodiment of the present invention;

[
Figure 2: A circuit diagram showing the signal switching circuit of the same embodiment device.

[Figure 3] Received signal waveform diagram in the same embodiment device,

[
FIG. 4 is a schematic configuration diagram of an ultrasonic flaw detection device using an ultrasonic probe and an ultrasonic diagnostic method according to another embodiment of the present invention,

[
Figure 5: A circuit diagram showing the signal switching circuit of the same embodiment device.

[Figure 6] Circuit diagram with an impedance matching coil added to the same signal switching circuit,

[Figure 7] Received signal waveform diagram in the same embodiment device,

[
Figure 8: Received signal waveform diagram when the impedance matching coil is removed in the same embodiment device,

[Figure 9] Schematic configuration diagram of a conventional ultrasonic flaw detection device,

FIG. 10 is a detection sensitivity characteristic diagram of the conventional device.

[Explanation of symbols]

4...Object to be measured, 7...Pulse generating circuit, 9...Receiving circuit, 1
0... Braun tube, 21... Ultrasonic wave, 22... Ultrasonic probe,
23, 45... Signal switching circuit, 24... Flaw detector, 25... Container, 26, 27, 41, 42... Vibrator, 30a, 30b,
30c, 44a, 44b, 44c, 44d...signal line, 3
1...terminal, 32...synchronous circuit.

Claims (2)

[Claims] Claim 1: A plurality of transducers built into the same container and stacked in a direction perpendicular to the mounting surface of the object to be measured, electrodes attached to both ends of each of the stacked transducers, and each of the stacked transducers. An ultrasonic probe equipped with multiple signal lines that guide signals sent and received from the electrodes to the outside of the container. [Claim 2] A plurality of vibrators stacked in a direction perpendicular to the mounting surface of the object to be measured are assembled in the same container, and signal lines are led out from the container from electrodes attached to both ends of each vibrator. , by simultaneously or alternately selecting a pair of signal wire combinations from among the derived signal wires, and applying a pulse signal between the selected pair of signal wires. An ultrasound diagnostic method that performs ultrasound diagnosis by injecting ultrasound waves having multiple different frequencies.