JP2000081421A - Damper for ultrasonic probe and ultrasonic probe having the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a damper having acoustic impedance that is almost equivalent to the acoustic impedance of a vibrator and an ultrasonic probe having the damper. SOLUTION: A damper 5 for damping ultrasonic waves transmitted from the surface of a vibrator 1 on which an electrode 11 is formed is provided on the surface. The damper 5 is fabricated by mixing particles having average particle diameters of 5 to 10 μm and having the same composition as a columnar piezoelectric substance contained in the vibrator 1, i.e., particles of PZT (lead zirconate titanate), into a hardenable resin such as epoxy resin, and has impedance almost equivalent to acoustic impedance which the vibrator 1 has.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe provided in, for example, an ultrasonic flaw detector and a damper for the ultrasonic probe.

[0002]

2. Description of the Related Art In an ultrasonic flaw detection method, an ultrasonic flaw detector provided with an ultrasonic probe is used to detect a state of damage occurring inside an object to be inspected. That is, by transmitting ultrasonic waves from the ultrasonic probe toward the inside of the device under test and observing reflected waves from the internal damage of the device under test, the internal damage of the device under test is monitored. Is detected.

[0003] An example of the configuration of an ultrasonic probe is disclosed in, for example, Japanese Utility Model Laid-Open No. 55-174158. The ultrasonic probe is provided with a transducer for converting an electric signal into an ultrasonic wave and converting the ultrasonic wave into an electric signal. The vibrator is formed in a flat plate shape using, for example, PZT (lead zirconate titanate) or lead titanate, and has one surface for transmitting and receiving ultrasonic waves to and from the object to be inspected. It is an ultrasonic wave transmitting / receiving surface. When an electric signal is input to the vibrator while the ultrasonic wave transmitting / receiving surface faces the surface of the inspection object, the vibrator is excited by the electric signal,
Ultrasonic waves are transmitted from the ultrasonic wave transmitting / receiving surface toward the inside of the subject. Then, when the transmitted ultrasonic wave is reflected by internal damage of the object to be inspected and enters the ultrasonic wave transmitting / receiving surface, the incident reflected wave is converted into an electric signal and output.
Therefore, it is possible to detect the position and the size of the internal damage of the inspection object based on the electric signal output from the vibrator.

[0004] Ultrasonic waves generated by the excitation of the vibrator are:
It is transmitted not only to the ultrasonic wave transmitting / receiving surface side but also to the opposite side to the ultrasonic wave transmitting / receiving surface. The ultrasonic wave transmitted to the side opposite to the ultrasonic wave transmitting / receiving surface has an adverse effect on the reflected wave from the object to be inspected, and causes a reduction in the resolution of the ultrasonic probe. Therefore, a damper for attenuating the ultrasonic wave transmitted to the side opposite to the ultrasonic wave transmitting / receiving surface is provided in close contact with the surface of the vibrator opposite to the ultrasonic wave transmitting / receiving surface.

[0005] The damper must have such a property that the ultrasonic wave transmitted to the side opposite to the ultrasonic wave transmitting / receiving surface is incident satisfactorily. Further, the damper must have a large propagation loss of the ultrasonic wave in order to rapidly attenuate the ultrasonic wave incident inside. In order to satisfy these two conditions, it is sufficient that the acoustic impedance of the damper is close to the acoustic impedance of the vibrator.

Conventional techniques for making the acoustic impedance of a damper close to the acoustic impedance of a vibrator are disclosed, for example, in Japanese Utility Model Laid-Open No. 55-179777 and Japanese Patent Laid-Open No. 2-2.
It is disclosed in 1850. These two publications have relatively large acoustic impedances (about 100 × 10
⁶ kg / m ² · s) is dispersed and mixed in an epoxy-based curable resin to form a damper, thereby obtaining 15 × 10 ⁶ kg / m ² · s and 1 × 10 ⁶ kg / m ² · s, respectively.
It is described that a damper having an acoustic impedance of 8.9 × 10 ⁶ kg / m ² · s could be obtained.

However, the acoustic impedance of the vibrator made of PZT is about 30 × 10 ⁶ kg / m ² ···
s, the acoustic impedance of the vibrator made of lead titanate is about 32 × 10 ⁶ kg / m ² · s, and the acoustic impedance of the damper and the acoustic impedance of the vibrator made by using the technique disclosed in the above publication. Are not approximate. Therefore, it is necessary to further increase the acoustic impedance of the damper, but it is difficult to make the acoustic impedance of the damper larger than each of the above-mentioned values with the technique described in the above publication.

[0008]

Therefore, by using a vibrator having a smaller acoustic impedance than a vibrator made of PZT or lead titanate, the acoustic impedance of the damper and the acoustic impedance of the vibrator can be approximated. Can be considered. As a vibrator having a relatively small acoustic impedance, a 1-3 piezoelectric composite can be cited. The 1-3 piezoelectric composite is formed by, for example, two-dimensionally arranging a plurality of thin columnar piezoelectric bodies made of PZT in a synthetic resin, and has an acoustic impedance of PZT in the composite. Of about 25% by volume fraction
0 × 10 ⁶ kg / m ² · s (JP-A-58-218)
No. 83, Electronic Ceramics Magazine 1986
March, page 50).

Therefore, in order to make the acoustic impedance of the damper formed by dispersing and mixing the tungsten powder in the epoxy-based curable resin close to the acoustic impedance of the 1-3 piezoelectric composite, the mixing ratio of the tungsten powder must be adjusted. It is necessary to reduce the acoustic impedance of the damper. However, when the mixing ratio of the tungsten powder is reduced, the tungsten powder settles in the resin due to a difference in specific gravity between the tungsten powder and the epoxy-based curable resin, and a good damper cannot be obtained.

Accordingly, an object of the present invention is to provide a damper having an acoustic impedance close to the acoustic impedance of a vibrator made of a 1-3 composite piezoelectric material, and an ultrasonic probe provided with this damper.

[0011]

Means for Solving the Problems The inventor of the present invention has conducted intensive studies in order to meet the above-mentioned problems, and has set a powder having the same composition as the columnar piezoelectric body contained in the 1-3 composite piezoelectric body with a curable resin. I thought about making a damper by mixing and molding in a box. By adjusting the mixing ratio of the powder and the curable resin, it has been found that the acoustic impedance of the damper can be made closer to the acoustic impedance of the 1-3 composite piezoelectric material.

That is, the invention according to claim 1 is provided on one surface of a vibrator made of a 1-3 composite piezoelectric element in which a plurality of columnar piezoelectric elements are arranged in a synthetic resin matrix in parallel and at equal intervals. An ultrasonic probe damper for attenuating ultrasonic waves transmitted from this surface, wherein a powder having the same composition as the columnar piezoelectric body is mixed in a curable resin and molded. A damper for an ultrasonic probe.

For example, the columnar piezoelectric body is made of PZT (silyl).
If it is composed of lead titanate),
The powder contained in the bumper is PZT powder. This PZT
The specific gravity of the powder is 7.5 g / cm^ThreeAnd the ratio of the curable resin
Weight is 1.0 to 2.2 g / cm ^ThreeSo even if cured
Even if the mixing ratio of PZT powder to the
No risk of PZT powder settling in the curable resin
No. Therefore, the mixing ratio between the PZT powder and the curable resin is automatically adjusted.
Can be adjusted freely, which results in the acoustic
Acoustic impedance almost equal to impedance
A good damper can be obtained.

Further, the damper having an acoustic impedance substantially equal to the acoustic impedance of the vibrator allows the ultrasonic wave transmitted from the vibrator to the damper to be satisfactorily incident on the inside thereof, Ultrasonic waves can be rapidly attenuated. As the curable resin,
Epoxy resin, silicon resin, or urethane resin can be used. However, it is preferable that the curable resin has the same composition as the synthetic resin contained in the vibrator, as described in claim 2, whereby the acoustic impedance of the damper is reduced. It can be made closer to the acoustic impedance of the child with high accuracy.

According to a third aspect of the present invention, there is provided a vibrator made of a 1-3 composite piezoelectric body in which a plurality of columnar piezoelectric bodies are arranged in a synthetic resin matrix in parallel with each other and at equal intervals. An ultrasonic probe including an ultrasonic probe damper. According to this configuration, the ultrasonic wave transmitted from the vibrator to the damper can be made to be incident on the inside of the damper satisfactorily, and the incident ultrasonic wave can be rapidly attenuated. When an ultrasonic probe is provided in an ultrasonic flaw detector for detecting the state of damage occurring inside the object to be inspected, ultrasonic waves transmitted from the transducer toward the damper are inspected. It is possible to suppress the adverse effect on the reflected wave from the inside of the body. Therefore, the resolution of the ultrasonic probe is improved.

In the 1-3 composite piezoelectric element, each columnar piezoelectric element is polarized in its height direction. Therefore, the vibrator made of the 1-3 composite piezoelectric material generates a potential difference between both end surfaces only when vibrated in the thickness direction (the height direction of the columnar piezoelectric material). Therefore, an ultrasonic probe equipped with this transducer
Only the reflected wave from the detected object can be satisfactorily converted into an electric signal, and the detection sensitivity is excellent.

Since each columnar piezoelectric body is polarized in the height direction, the vibrator is excited only in the thickness direction when a voltage is applied between both end faces. Therefore, the generation of noise due to the vibrator being excited in the direction orthogonal to the thickness direction is small, and the longitudinal wave can be transmitted favorably to the test object. The invention according to claim 4 is the ultrasonic probe according to claim 3, wherein the columnar piezoelectric body is formed in a columnar shape.

The columnar piezoelectric body formed in a cylindrical shape has no anisotropy in the radial direction. Therefore, the vibrator using the columnar piezoelectric body is a vibrator using the piezoelectric body formed in a prismatic shape.
As compared with a vibrator made of a −3 composite piezoelectric body, noise is less likely to be generated due to excitation in the radial direction.

[0019]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 is a sectional view showing the internal configuration of an ultrasonic probe according to one embodiment of the present invention. This ultrasonic probe is provided in an ultrasonic flaw detector for detecting a state of damage occurring inside an object to be inspected, and has a vibrator 1 made of a 1-3 composite piezoelectric body. ing. The vibrator 1 is formed, for example, in a flat cylindrical shape, and the electrodes 11, 1 are formed on both end surfaces thereof by, for example, vacuum-depositing silver, nickel, or the like.
2 are formed.

The vibrator 1 is housed in a case 2 in which a space is formed and one end surface (the lower surface in FIG. 1) is open. A connector 32 connected to an ultrasonic flaw detector main body (not shown) via a cable 31 is provided through the closed end face of the case 2.
Two lead wires 33 and 34 are drawn out of the connector 32, and the tips of the lead wires 33 and 34 are connected to the electrodes 11 and 12 formed on the vibrator 1, respectively. Therefore, when the electric signal is transmitted from the ultrasonic flaw detector main body, the transmitted electric signal is given to the vibrator 1 via the cable 31, the connector 32 and the leads 33 and 34, and the vibrator 1 , A potential difference is generated between both end faces, and the vibrator 1 is excited by the potential difference.

The surface of the vibrator 1 on which the electrodes 12 are formed transmits an ultrasonic wave generated by the excitation of the vibrator 1 toward the inside of the device under test, and reflects a reflected wave from the inside of the device under test. Of the ultrasonic wave for receiving the wave. The ultrasonic wave transmitting / receiving surface is bonded to a matching layer 4 provided so as to close the open end face of the case 2. Matching layer 4
Is for matching the acoustic impedance between the vibrator 1 and the device under test and preventing the vibrator 1 from directly contacting the device under test and being damaged. It is preferable to have an acoustic impedance of about an intermediate value between the acoustic impedance of the test object and the acoustic impedance of the test object. Matching layer 4 can be made of, for example, alumina or tungsten carbide when the object to be inspected is made of metal, and can be made of, for example, epoxy resin or urethane when the object to be inspected is a human body. It can be composed of a system resin.

A damper 5 for attenuating an ultrasonic wave transmitted to the surface of the vibrator 1 on which the electrode 11 is formed is provided inside the case 2 on the surface of the vibrator 1 on which the electrode 11 is formed. It is provided in close contact with. The damper 5 has the same composition as the columnar piezoelectric body included in the vibrator 1 and has an average particle size of 5 μm to 5 μm.
It is made by mixing a powder of 10 μm, that is, a powder of PZT (lead zirconate titanate) in a curable resin such as an epoxy resin, and has an impedance substantially equal to the acoustic impedance of the vibrator 1. have.
Therefore, the ultrasonic wave transmitted to the surface of the vibrator 1 on which the electrode 11 is formed can be satisfactorily incident on the inside of the damper 5, and the incident ultrasonic wave can be rapidly attenuated. .

Reference numeral 6 is for holding the vibrator 1, the matching layer 4, and the damper 5 at predetermined positions in the case 2. According to the above configuration, in a state where the outer surface of the matching layer 4 is in close contact with the inspection object, an electric signal is input to the vibrator 1 from the ultrasonic flaw detector main body (not shown), and the vibrator 1 is excited. Then, an ultrasonic wave is transmitted toward the inside of the test object via the matching layer 4. The transmitted ultrasonic wave is reflected on the inside of the object to be inspected or reflected at an end face of the object to be inspected, and returns to the transducer 1 from the inside of the object to be inspected via the matching layer 4. The reflected wave incident on the vibrator 1 is converted into an electric signal by the vibrator 1 and input to the ultrasonic flaw detector main body via the leads 33 and 34, the connector 32 and the cable 31. Then, the internal state of the object to be inspected is displayed on the display provided in the ultrasonic flaw detector main body, whereby the position and size of the internal damage of the object to be inspected can be detected.

In this embodiment, the damper 5 is made by mixing powder having the same composition as the piezoelectric body contained in the vibrator 1 into a curable resin such as an epoxy resin. Since the specific gravity of the epoxy resin is 1.4 g / cm ³ and the specific gravity of the PZT powder is 7.5 g / cm ³ ,
Even if the mixing ratio of the PZT powder to the curable resin is small, there is no possibility that the PZT powder will settle in the curable resin. Therefore, the mixing ratio of the PZT powder and the curable resin can be freely adjusted as described above, whereby a good damper 5 having an acoustic impedance substantially equal to the acoustic impedance of the vibrator 1 can be obtained. Can be. In order to increase the acoustic impedance of the damper 5, it is only necessary to increase the mixing amount of the PZT powder in the curable resin, and to reduce the acoustic impedance, it is necessary to mix the PZT powder in the curable resin. The amount may be reduced.

Further, the damper 5 having an acoustic impedance substantially equal to the acoustic impedance of the vibrator 1 allows the ultrasonic wave transmitted to the surface of the vibrator 1 on which the electrode 11 is formed to be satisfactorily incident on the inside. And the incident ultrasonic waves can be rapidly attenuated. This suppresses the ultrasonic wave transmitted to the surface of the transducer 1 on which the electrode 11 is formed, that is, the side opposite to the ultrasonic wave transmitting / receiving surface, from adversely affecting the reflected wave from inside the test object. As a result, the resolution of the ultrasonic probe can be improved.

FIG. 2 is a cross-sectional view showing the structure of the vibrator 1 and shows a state where the vibrator 1 is cut along a plane parallel to an end face thereof. The vibrator 1 has a 1-3 connection structure in which a plurality of columnar piezoelectric bodies 14 made of PZT are arranged in parallel and at equal intervals in a matrix 13 made of a synthetic resin such as an epoxy resin. Such 1-3
The vibrator 1 made of a composite piezoelectric body can be produced, for example, as follows. First, a plurality of (32 in this embodiment) columnar piezoelectric piezoelectric bodies are cut on a circular substrate by cutting a flat PZT sintered body that has been polarized in the thickness direction using an ultrasonic machine. A PZT workpiece in which the bodies 14 stand upright and parallel to each other is created. Next, the PZT processed product thus obtained is fitted into a mold, and a synthetic resin as a material of the matrix 13 is poured into the mold. Then, after the poured synthetic resin is sufficiently cured, the PZT processed product and the cured synthetic resin are taken out of the mold, and the vibrator 1 is obtained by cutting off the circular substrate on the bottom surface.

In the vibrator 1 thus produced, each columnar piezoelectric body 14 is polarized in the height direction (the thickness direction of the vibrator 1). Therefore, the vibrator 1 generates a potential difference between both end surfaces only when vibrated in the thickness direction. Therefore,
The vibrator 1 can satisfactorily convert only the reflected wave from the detected object into an electric signal, and can improve the detection sensitivity of the ultrasonic probe.

Since each columnar piezoelectric body 14 is polarized in the height direction, the vibrator 1 is excited only in the thickness direction when a voltage is applied between both end faces. Therefore, the vibrator 1 is in the radial direction (the direction orthogonal to the thickness direction).
The generation of noise due to the excitation of the longitudinal wave is small, and the longitudinal wave can be satisfactorily transmitted toward the test object. In addition, since the columnar piezoelectric body 14 has no anisotropy in the radial direction, the vibrator 1 using the columnar piezoelectric body 14 is different from a 1-3 composite piezoelectric body using a prism-shaped piezoelectric body. In comparison, the generation of noise due to radial excitation is further reduced.

The synthetic resin forming the matrix 13 may be, for example, a silicone resin or a urethane resin in addition to the epoxy resin described above.
In the above-described embodiment, the damper 5 is formed by mixing powder having the same composition as the piezoelectric body included in the vibrator 1, that is, PZT powder in a curable resin such as an epoxy resin. However, as the curable resin, for example, a silicon resin or a urethane-based resin can be used in addition to the epoxy resin. However, as the curable resin forming the damper 5, it is preferable to use the same resin as the synthetic resin forming the matrix 13 of the vibrator 1, so that the acoustic impedance of the vibrator 1 and the acoustic impedance of the damper 5 are reduced. Can be approximated with higher accuracy.

Furthermore, the average particle size of the PZT powder contained in the damper 5 is 5 μm to 10 μm, but any PZT powder having an average particle size of 1 μm to 100 μm can be used. In addition, various design changes can be made within the scope of the technical matters described in the claims.

[0031]

Next, a more specific embodiment will be described. <Vibrator (1-3 Composite Piezoelectric Material)> As the vibrator, a vibrator was prepared in which 32 cylindrical piezoelectric materials having a diameter of 1 mm and made of PZT in an epoxy resin were regularly arranged at a pitch of 1.48 mm. The diameter of the whole vibrator is 12 mm, the volume fraction of PZT to the whole vibrator is 30%,
The density of the vibrator is 3.08 g / cm ³ . Also, when the sound speed in this vibrator was measured, a result of a sound speed of 2770 m / s was obtained. Therefore, the acoustic impedance (density × sound speed) of this vibrator is about 8.53 × 10 ⁶ k
g / m ² · s.

<Damper (Example)> A mixture obtained by mixing 20 g of PZT powder (manufactured by CERATECH) having an average particle size of 5 mm to 10 mm with 5.5 g of epoxy resin (manufactured by Maruto, product name: Tropoxy 154). Is sufficiently degassed and then filled into a silicone resin mold, and 3 degrees at 120 degrees.
The material was cured by heating for 0 minutes to obtain a damper. The density of the damper thus obtained was 2.64 g / cm ³ . Also,
When the sound speed in this damper is measured, the sound speed is 1924 m /
The result s was obtained. Therefore, the acoustic impedance of this damper is about 5.08 × 10 ⁶ kg / m ² · s
And the acoustic impedance 8.53 of the vibrator described above.
It was confirmed that it was close to × 10 ⁶ kg / m ² · s.

The above contents are summarized in Table 1 below.

[0034]

[Table 1] <Observation of Reflected Waveform> Ultrasonic waves were incident on one surface of the damper obtained as described above, and the reflected waveform reflected on the end surface facing the one surface and returned to the one surface was observed with an oscilloscope. FIG. 3 shows a reflection waveform observed when an ultrasonic wave having a frequency of 20 MHz was incident on the damper, and a frequency of 1 M
FIG. 4 shows a reflection waveform observed when an ultrasonic wave of Hz is incident on the damper. From FIG. 3 and FIG.
When an ultrasonic wave of 1 MHz is incident, the incident wave is attenuated so that the reflected waveform cannot be observed, and even when an ultrasonic wave of a low frequency of 1 MHz is incident, it can be confirmed that the amplitude of the reflected waveform is considerably small.

For comparison, a solder having a diameter of 1 was used.
A columnar solder damper having a thickness of 9.7 mm and a thickness of 19.8 mm was manufactured, and similarly to the damper according to this example, an ultrasonic wave having a frequency of 1 MHz was incident on the solder damper, and its reflected waveform was observed with an oscilloscope. FIG. 5 shows the observation results. The density of the solder damper was 8.77 g / cm ³ , the sound velocity in the solder damper was 2682 m / s, and the acoustic impedance was calculated to be about 23.52 × 10 ⁶ kg / m ^2.
-It was s. From the reflected waveforms shown in FIGS. 4 and 5, it can be confirmed that the damper made of solder has a small attenuation of the incident wave, whereas the damper according to this embodiment has a large attenuation of the incident wave.

[0036]

According to the present invention, the acoustic impedance of the damper can be made substantially equal to the acoustic impedance of the vibrator. A damper having an acoustic impedance substantially equal to the acoustic impedance of the vibrator enables the ultrasonic waves transmitted from the vibrator to the damper to be satisfactorily incident on the inside, and the incident ultrasonic waves can be quickly transmitted. Can be attenuated. Therefore, the ultrasonic probe equipped with such a damper has a resolution in which the ultrasonic wave transmitted from the transducer toward the damper side has an adverse effect on the reflected wave from the inside of the test object. Will be high.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing an internal configuration of an ultrasonic probe according to one embodiment of the present invention.

FIG. 2 is a cross-sectional view illustrating an internal configuration of a vibrator.

FIG. 3 is a diagram illustrating a reflected waveform observed when a 20 MHz ultrasonic wave is incident on the damper according to the example.

FIG. 4 is a diagram illustrating a reflection waveform observed when 1 MHz ultrasonic waves are incident on the damper according to the example.

FIG. 5 is a diagram showing a reflection waveform observed when a 1 MHz ultrasonic wave is incident on a solder damper as a comparative example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Oscillator 13 Matrix 14 Columnar piezoelectric body 5 Damper

Claims (4)

[Claims] 1. A vibrator made of a 1-3 composite piezoelectric body in which a plurality of columnar piezoelectric bodies are arranged in parallel at equal intervals in a synthetic resin matrix, and waves are transmitted from this plane. An ultrasonic probe damper for attenuating ultrasonic waves, characterized in that a powder having the same composition as the columnar piezoelectric body is mixed in a curable resin and molded. Probe damper. 2. The ultrasonic probe damper according to claim 1, wherein said curable resin has the same composition as a synthetic resin contained in said vibrator. 3. A vibrator made of a 1-3 composite piezoelectric body in which a plurality of columnar piezoelectric bodies are arranged in parallel at equal intervals in a synthetic resin matrix, and for an ultrasonic probe according to claim 1 or 2. An ultrasonic probe comprising a damper. 4. The ultrasonic probe according to claim 3, wherein said columnar piezoelectric body is formed in a columnar shape.