JPH0746693A - Ultrasonic transducer and manufacture therefor - Google Patents

Abstract

PURPOSE:To easily obtain an ultrasonic transducer which is suitable to a high output/miniaturization. CONSTITUTION:An ultrasonic transducer 5 is composed of a thin-layer piezoelectric element 1 and two resonance bodies 2a and 2b holding this element 1. On the surface of one resonance body 2a, an acoustic matching layer 3 is formed, and the surface is made an acoustic radiation surface 6. On the surface of the other resonance body 2b, a rear load member 4 is formed. In the two resonance bodies 2a and 2b, the flat surface shapes are formed larger than that of the thin-layer piezoelectric element 1. The end faces of the both of the resonance bodies 2a and 2b are jointed to the thin-layer piezoelectric element 1 and are jointed by joint resin whose linear shrinkage ratio is large at the time of curing at the outer peripheral side of the thin-layer piezoelectric element 1.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic transducer used in a medical or nondestructive ultrasonic diagnostic apparatus.

[0002]

2. Description of the Related Art Conventionally, the structure of an ultrasonic transducer is described in "Medical Ultrasonic Equipment Handbook", Corona Company, p1.
As shown in 86 and the like, a PZT piezoelectric ceramic thin piece having electrodes formed on both sides of the damping layer was bonded via an insulating layer, and an acoustic matching layer was further bonded.

[0003]

However, there is a growing demand for medical ultrasonic endoscopes capable of diagnosing pancreatic ducts, circulatory organs, etc., and industrial ultrasonic diagnostic equipment for non-destructive inspection of thin tubules. In order to realize the above, the outer diameter becomes as small as about 1 to several mm, so that the ultrasonic transducer mounted on this also needs to be downsized at the same time. In this case, since the sensitivity of the ultrasonic transducer is proportional to the square of the area of the acoustic radiation surface, the sensitivity becomes very small.

When a drive voltage is applied to the ultrasonic transducer and the electrical impedances of the signal transmission system for transmitting the signal received by the ultrasonic transducer to the observation device match, the sensitivity of the entire system composed of them is It will be the maximum. However, when the outer diameter is reduced as described above, the electrical impedance of the piezoelectric element is several times as large as that of the signal transmission system, which is generally about 50Ω. This phenomenon remarkably occurs particularly in PT type piezoelectric ceramics and polymer type piezoelectric materials.

For this reason, a loss occurs at the connection between the two, which is a cause of further lowering the sensitivity. In addition, this phenomenon causes a loss of transmission even in an ultrasonic transducer having a larger area, since the electrical impedance of the ultrasonic transducer is small.

Therefore, the present invention was developed in view of the above-mentioned drawbacks in the prior art, and an object thereof is to provide an ultrasonic transducer suitable for high output and a method for manufacturing the same.

[0007]

SUMMARY OF THE INVENTION The present invention is directed to a piezoelectric vibrator, an acoustic matching layer formed on one surface of the piezoelectric vibrator, and a back load material formed on the other surface of the piezoelectric vibrator. In an ultrasonic transducer having as a basic component, the piezoelectric vibrator is sandwiched between a thin-layer piezoelectric element and the piezoelectric element with a crimping force, and two resonances are integrally fixed to the piezoelectric element. It is configured as a thickness direction ultrasonic resonator including a body.

Further, a piezoelectric vibrator, an acoustic matching layer formed on one surface of the piezoelectric vibrator, and a back load material formed on the other surface of the piezoelectric vibrator are used as basic constituent elements. In the method for manufacturing a sound wave transducer, the piezoelectric vibrator is formed by bonding a resonator whose planar shape is larger than the piezoelectric element to both surfaces of a thin-layer piezoelectric element, and at the time of curing on the outer periphery of the piezoelectric element. It is a manufacturing method in which both the resonators are bonded to each other with an adhesive having a large linear shrinkage.

[0009]

In the present invention, the mechanical Q is increased and the output is increased by the thickness direction resonator. Further, by tapering the shape of the resonator, the degree of freedom in setting the shape of the piezoelectric element can be increased while keeping the size of the acoustic radiation surface constant. This makes it possible to align the electrical impedance of the piezoelectric element with the signal transmission system, and eliminates signal transmission loss.

[0010]

Embodiment 1 FIGS. 1 to 3 show this embodiment, FIG. 1 is a longitudinal sectional view, and FIGS. 2 and 3 are graphs. The ultrasonic transducer 5 includes a thin layer piezoelectric element 1 having electrodes formed on the surface of a piezoelectric thin layer made of PZT, and the thin layer piezoelectric element 1.
A piezoelectric vibrator composed of two resonators 2a and 2b made of alumina ceramics sandwiching
The acoustic matching layer 3 is formed on the surface of one of the resonators 2a so that the surface serves as an acoustic radiation surface 6, while the other resonator 2b is formed.
The back load member 4 was formed on the surface of the above.

The two resonators 2a and 2b are larger in planar shape than the thin layer piezoelectric element 1.
The two resonators 2a and 2b are joined at their end faces to the thin layer piezoelectric element 1 by a low-viscosity type epoxy adhesive, and at the outer periphery of the thin layer piezoelectric element 1 an epoxy having a large linear shrinkage factor when cured. They are bonded to each other by a bonding resin 7 made of a system adhesive.

In the present invention, the resonators 2a and 2b are pressed against each other due to the linear contraction of the bonding resin 7 during curing. As a result, the thin-layer piezoelectric element 1 is held by the resonators 2a and 2b while being applied with a crimping force. Therefore, the resonators 2a, 2b and the thin layer piezoelectric element 1 operate as an ultrasonic resonator integrated with each other.

According to this embodiment, since the compression force is applied to the thin layer piezoelectric element 1, the ultrasonic transducer 5
The overall Qm is increased, resulting in a high-power ultrasonic transducer. In order to drive this type of ultrasonic transducer, in addition to the commonly used drive waveform as shown in FIG.
It is also possible to use a waveform on only one side of the sinusoidal curve as shown in FIG. In this case, the resonance action is strengthened, resulting in higher output.

In this embodiment, the case where the PZT type piezoelectric ceramics is used as the piezoelectric element is shown, but other perovskite type piezoelectric ceramics such as the PT type, the polymer piezoelectric material and the crystal type piezoelectric material are used. It can also be used. Further, by making the piezoelectric element hollow, it is possible to simultaneously bond both resonators on the inner and outer circumferences of the piezoelectric element. Further, it is needless to say that it is possible to bond the piezoelectric element and the resonator and the bonding between the resonators at the same time by using an adhesive that has a low viscosity and a large linear contraction rate during curing. Yes.

Similarly, in the present embodiment, the material of the resonator is alumina ceramics, but in addition to this, for example, zirconia ceramics, machinable ceramics, copper alloys such as phosphor bronze, and metals such as stainless steel are used. It is possible to use an elastic material having a small sound wave attenuation. Also, the adhesive of the bonding resin and the piezoelectric element is an epoxy adhesive,
Anaerobic adhesives and urethane / acrylic / phenolic resins can also be used.

[0016]

Embodiment 2 FIGS. 4 to 6 show this embodiment, FIG. 4 is a perspective view, FIG. 5 is a longitudinal sectional view, and FIG. 6 is a side view. The basic configuration is the same as that of the first embodiment, and the differences will be described.
For this reason, the same members as those in the first embodiment are designated by the same reference numerals in the drawings.

In this embodiment, the resonator 2a on the acoustic radiation surface 6 side is provided.
An ultrasonic transducer 5 having a cross-sectional area reduction type horn 8 formed integrally therewith, an acoustic matching layer 3 formed on an end surface of the cross-sectional area reduction type horn 8, and an acoustic radiation surface 6 is provided. Further, FIG. 6 shows a case where an acoustic mirror 11 is added to the ultrasonic transducer 5 via a vibration insulating member 12.

In the present embodiment, the ultrasonic pulse generated by applying the drive signal to the thin layer piezoelectric element 1 is transmitted to the acoustic matching layer 3 by the sectional area reduction type horn 8 while its amplitude is amplified. The sound is emitted from the sound emitting surface 6.

Further, in the example of using the mirror shown in FIG. 6, the ultrasonic pulse emitted from the acoustic emission surface 6 is radiated to the outside after its path is changed by the acoustic mirror 11. At this time, the vibration of the resonator 2a is caused by the vibration insulation member 1
2 does not propagate to the mirror 11.

According to this embodiment, the acoustic radiation surface can be reduced to any size. In this case, the ultrasonic pulse has a reduced emission area but an increased displacement, so that no loss occurs as a whole. Therefore, when the outer diameter W shown in FIG. 6 is regulated, the area of the piezoelectric element can be maximized under the condition that the acoustic radiation surface is contained within the outer diameter W.

Further, as described above, the areas of the piezoelectric element and the acoustic radiation surface can be individually set arbitrarily. Therefore, the electrical impedance at the resonance frequency of the piezoelectric element can be made the same as that of the signal transmission system while the shape of the acoustic radiation surface is kept in conformity with the use of the product equipped with the ultrasonic transducer. Therefore, it is possible to eliminate a loss related to signal transmission. As a result, the output / total sensitivity of the ultrasonic transducer and the degree of freedom in design can be increased.

In this embodiment, the case where the whole shape of the ultrasonic transducer is cylindrical is shown, but it is obvious that the same can be applied to a prism and the like.

[0023]

Third Embodiment FIGS. 7 and 8 show the present embodiment, FIG. 7 is a perspective view, and FIG. 8 is a longitudinal sectional view. The basic configuration is similar to that of the first embodiment, and the differences will be described. Due to this freedom, the same members as those in the first embodiment are numbered the same in the drawings.

In this embodiment, the resonator 2a on the acoustic radiation surface 6 side is provided.
An ultrasonic cross-sectional area expansion type horn 9 is formed integrally therewith, and an acoustic matching layer 3 is formed on the end surface of the expanded cross-sectional area type horn 9 to provide an ultrasonic transducer 5 having an acoustic radiation surface 6.

In the present embodiment, the ultrasonic pulse generated by applying the drive signal to the thin layer piezoelectric element 1 by the expanded cross sectional area type horn 9 is applied to the acoustic matching layer 3 while the area of its vibrating surface is expanded. It is transmitted and emitted from the acoustic emission surface 6.

According to this embodiment, the acoustic radiation surface 6 can be enlarged to any size. In this case, the ultrasonic pulse has a reduced displacement but an increased radiation area, so that no loss occurs as a whole. If the area of the acoustic radiation surface is large, the sound source becomes a planar sound source, so that the ultrasonic beam oscillated from the ultrasonic transducer becomes difficult to diverge. For this reason, the resolution particularly in the direction orthogonal to the ultrasonic beam is improved.

Further, as described above, the areas of the piezoelectric element and the acoustic radiation surface can be individually set arbitrarily. Therefore, the electrical impedance at the resonance frequency of the piezoelectric element can be made the same as that of the signal transmission system while the shape of the acoustic radiation surface is kept in conformity with the use of the product equipped with the ultrasonic transducer. Therefore, it is possible to eliminate a loss related to signal transmission. These can increase the output, overall sensitivity and resolution of the ultrasonic transducer.

[0028]

Fourth Embodiment FIG. 9 is a vertical cross-sectional view showing this embodiment. The basic configuration is the same as that of the third embodiment, and the differences will be described. For this reason, the same members as those in the third embodiment are designated by the same reference numerals in the drawings.

In this embodiment, the resonator 2a on the acoustic radiation surface 6 side is provided.
And a concave surface 10 is formed on an end surface of the expanded cross sectional area type horn 9, and an acoustic matching layer 3 is formed on the concave surface 10 to form an acoustic radiation surface 6. The provided ultrasonic transducer 5 was used.

In this embodiment, the ultrasonic beam oscillated from the concave surface is focused and emitted from the acoustic emission surface 6.

According to this embodiment, the ultrasonic beam for operating the inside of the observation object becomes thin, so that the resolution in the direction orthogonal to the ultrasonic beam is improved.

In this embodiment, only the case where it is applied to the ultrasonic transducer having the structure shown in the third embodiment has been described, but it goes without saying that it can be applied to each of the above embodiments.

[0033]

As described above, according to the ultrasonic transducer and the manufacturing method thereof according to the present invention, it is possible to easily realize an ultrasonic transducer suitable for high output and miniaturization.

[Brief description of drawings]

FIG. 1 is a vertical sectional view showing a first embodiment.

2 is a graph showing Example 1. FIG.

FIG. 3 is a graph showing Example 1.

FIG. 4 is a perspective view showing a second embodiment.

FIG. 5 is a vertical sectional view showing a second embodiment.

FIG. 6 is a side view showing a second embodiment.

FIG. 7 is a perspective view showing a third embodiment.

FIG. 8 is a vertical sectional view showing a third embodiment.

FIG. 9 is a vertical sectional view showing a fourth embodiment.

[Explanation of symbols]

 1 Thin Layer Piezoelectric Element 2 Resonator 3 Acoustic Matching Layer 4 Back Load Material 5 Ultrasonic Transducer 6 Acoustic Radiation Surface 7 Bonding Resin 8 Reduced Area Horn 9 Reduced Area Horn 10 Concave 11 Mirror 12 Acoustic Insulation Member

Claims (2)

[Claims] 1. A supersonic device comprising a piezoelectric vibrator, an acoustic matching layer formed on one surface of the piezoelectric vibrator, and a back load material formed on the other surface of the piezoelectric vibrator as basic constituent elements. In a sound wave transducer, the piezoelectric vibrator includes a thin-layer piezoelectric element and two resonators sandwiching the piezoelectric element with a crimping force and integrally fixed to the piezoelectric element. An ultrasonic transducer characterized by being configured as an acoustic wave resonator. 2. A piezoelectric vibrator, an acoustic matching layer formed on one surface of the piezoelectric vibrator, and a back load material formed on the other surface of the piezoelectric vibrator as a basic constituent element. In the method for manufacturing a sound wave transducer, the piezoelectric vibrator is formed by bonding a resonator whose planar shape is larger than the piezoelectric element to both surfaces of a thin-layer piezoelectric element,
An ultrasonic transducer manufacturing method, characterized in that the piezoelectric element is formed by bonding the two resonators to each other with an adhesive having a large linear shrinkage ratio when cured on the outer periphery of the piezoelectric element.