JP2007033140A - Ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe usable in a civil engineering structure or the like and enhanced in sensitivity. <P>SOLUTION: The ultrasonic probe 1 is constituted so that a piezoelectric vibrator 3 is vibrated when transmission voltage Vs is applied across electrodes 5 and 7. The vibration of the piezoelectric vibrator 3 is transmitted through an aluminum front plate 9 and a medium being a specimen as an ultrasonic wave F<SB>0</SB>. In the case of inspection due to a reflecting method, the ultrasonic wave F<SB>0</SB>is reflected from the boundary surface of the specimen, the reflected wave is received by the ultrasonic probe 1 and receiving voltage Vr is generated in the piezoelectric vibrator 3. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe.

  In ultrasonic nondestructive inspection of civil engineering structures such as concrete, mortar, and bricks, it is necessary to use ultrasonic waves at a frequency of about 100 kHz, which are lower than conventional metal flaw detection and human body ultrasonic diagnosis. This is because, at high frequencies, the attenuation of ultrasonic waves increases and cannot be used (see, for example, [Patent Document 1]).

Japanese Patent Laid-Open No. 5-180812

  FIG. 8 shows a conventional ultrasonic probe 101. As shown in FIG. 8, in the conventional ultrasonic probe 101, a piezoelectric vibrator 103 is provided between an electrode 105 and an electrode 107, a front plate 109 made of iron is provided on the electrode 107, and a damper is provided on the electrode 105. 111 is provided.

  However, when the above-described structure (hereinafter referred to as a subject) is inspected using the ultrasonic probe 101 shown in FIG. 8, the acoustic impedance of the subject is high (the acoustic impedance of concrete is about 10.5). [Mrayl]), since the surface of the subject is extremely rough, the ultrasonic probe 101 is easily damaged during use, and there is a problem that the ultrasonic wave cannot be efficiently emitted into the subject. In addition, there is a problem that ultrasonic wave absorption by the damper 111 of the ultrasonic probe 101 is small, unnecessary reflection from the damper 111 occurs, and a necessary frequency characteristic of the ultrasonic probe cannot be obtained.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to provide an ultrasonic probe that can be used for civil engineering structures and the like and has high sensitivity.

In order to achieve the above-described object, the present invention includes a piezoelectric vibrator provided between a pair of electrodes and a front plate provided on one side of the piezoelectric vibrator, and an acoustic impedance of the front plate. Is
15 ± 15 × 0.2 (Mrayl)
It is an ultrasonic probe characterized by being.

The front plate is, for example, aluminum. When the wavelength of the sound wave in the front plate is λ, the thickness d of the front plate is:
d = λ / 4 ± λ / 16
It is desirable that

  ADVANTAGE OF THE INVENTION According to this invention, it can be used for civil engineering structures etc., and an ultrasonic probe with high sensitivity can be provided.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings. FIG. 1 shows an ultrasonic probe 1 according to the present invention. As shown in FIG. 1, the ultrasonic probe 1 is provided with a piezoelectric vibrator 3 between an electrode 5 and an electrode 7, and a front plate 9 is provided on the electrode 7.

  The piezoelectric vibrator 3 vibrates when a voltage is applied to the electrodes 5 and 7 and outputs ultrasonic waves to the inside of the subject. The front plate 9 is an ultrasonic radiation surface.

  The front plate 9 is made of a material having an acoustic impedance of 15 ± 15 × 0.2 (Mrayl), for example, aluminum. The acoustic impedance of aluminum is 17 (Mrayl). If the acoustic impedance of the front plate is 15 ± 15 × 0.2 (Mrayl), a material other than aluminum may be used.

  When the voltage Vs is applied between the electrode 5 and the electrode 7, the piezoelectric vibrator 3 vibrates. The vibration of the piezoelectric vibrator 3 is transmitted to the front plate 9, and ultrasonic waves are emitted from the ultrasonic probe 1 into the subject.

  For example, when the inspection is performed by the reflection method, when the transmission voltage Vs is applied to the ultrasonic probe 1, ultrasonic waves are emitted in the subject. The ultrasonic wave is reflected by the boundary surface of the subject, the reflected wave is received by the ultrasonic probe 1, and a reception voltage Vr is generated in the piezoelectric vibrator 3.

  Next, the transmission / reception characteristics (VTG characteristics) (Voltage Transfer Gain characteristics) will be described with reference to FIGS.

The transmission / reception wave characteristic (VTG characteristic) is expressed as a ratio of the reception voltage and the transmission voltage, and is expressed in decibels. When the reception voltage is Vr and the transmission voltage is Vs, it is expressed by equation (1).
VTG = 20LOG (Vr / Vs) (1)

FIG. 2 shows the relationship between the transmission frequency (Frequency), the thickness (thickness) of the aluminum front plate 9, and the VTG.
In FIG. 2, the frequency (Frequency) is obtained by dividing the frequency of the ultrasonic wave emitted from the ultrasonic probe 1 by the center frequency f ₀ of the ultrasonic probe to make it dimensionless. As for the thickness (thickness), “1” indicates λ / 4 (λ is the wavelength of the ultrasonic wave in the front plate 9 or aluminum), and “1.5” indicates λ / 4 × 1.5 of the front plate 9. Indicates double.

FIG. 3 is a two-dimensional graph showing the cut end of the front plate 9 having a specific thickness.
Generally speaking, as shown in FIG. 3, for a certain thickness of the front plate 9, there is a frequency band A where the VTG value is large, centered on the frequency “1”. The wider the frequency band A where the VTG value is larger, the less unnecessary reflected waves are generated. Further, the smaller B is, the smaller the loss of the reception voltage with respect to the transmission voltage.

  4 to 7 compare the relationship between the frequency and the VTG in the cut surface when the thickness of the front plate 9 is changed in the graph of FIG. 2, that is, the four types of thicknesses of the front plate 9.

  As shown in FIGS. 4 to 7, when the thickness of the front plate 9 is changed, the shape of the cut, that is, the curve indicating the relationship between the frequency and the VTG also changes.

  As shown in FIG. 4 to FIG. 7, the frequency band in which the numerical value of VTG becomes maximum is wide before and after (thickness = 1.0). When the thickness of the front plate 9 is large (thickness = 1.2) or small (thickness = 0.8), the frequency band in which the VTG value is maximum becomes narrow.

And the thickness d of the front plate 9 is
d = λ / 4 ± λ / 16
It was found that the transmission / reception frequency band of the ultrasonic probe 1 could be flattened and the sensitivity would be good if the degree was about.

  As described above, according to the present embodiment, by adopting aluminum for the front plate 9, the transmission / reception frequency band of the ultrasonic probe 1 can be flattened, the sensitivity can be improved, and the civil engineering structure can be obtained. Can also be used. Furthermore, the manufacturing cost can be reduced by eliminating the damper 111.

  The preferred embodiments of the ultrasonic probe according to the present invention have been described above with reference to the accompanying drawings, but the present invention is not limited to such examples. It will be apparent to those skilled in the art that various changes or modifications can be conceived within the scope of the technical idea disclosed in the present application, and these are naturally within the technical scope of the present invention. Understood.

Schematic diagram showing the configuration of the ultrasound probe 1 Graph showing the transmission and reception characteristics of aluminum front plate 9 A graph showing the characteristics of the front plate 9 having a specific thickness The figure which shows the wave transmission / reception characteristic when the thickness of the front plate 9 is changed The figure which shows the wave transmission / reception characteristic when the thickness of the front plate 9 is changed The figure which shows the wave transmission / reception characteristic when the thickness of the front plate 9 is changed The figure which shows the wave transmission / reception characteristic when the thickness of the front plate 9 is changed The figure which shows the conventional structure of the ultrasound probe 1

Explanation of symbols

1 ... Ultrasonic probe 3 ... Piezoelectric transducer 5, 7 ... Electrode 9 ... Front plate

Claims (3)

A piezoelectric vibrator provided between a pair of electrodes;
A front plate provided on one side of the piezoelectric vibrator;
Comprising
The acoustic impedance of the front plate is
15 ± 15 × 0.2 (Mrayl)
Ultrasonic probe characterized by being.   The ultrasonic probe according to claim 1, wherein the front plate is made of aluminum. When the wavelength of the sound wave in the front plate is λ,
The thickness d of the front plate is
d = λ / 4 ± λ / 16
The ultrasonic probe according to claim 1, wherein:

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