JPH04273698A - Ultrasonic wave probe - Google Patents

Abstract

PURPOSE:To attain broad band processing and high resolution without deteriorating the sensitivity regardless of the use of a composite piezoelectric body. CONSTITUTION:A piezoelectric vibrator is formed to be a laminate structure comprising a piezoelectric ceramic layer 13, a piezoelectric ceramic member 16 and a resin material 17, and the piezoelectric ceramic layer 13 is arranged toward a packing member 11 and the composite piezoelectric layer 14 is arranged toward an ultrasonic wave transmission reception wave side respectively.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an ultrasonic probe used in an ultrasonic inspection device, and more particularly to a piezoelectric vibrator for transmitting and receiving ultrasonic waves.

0002

[Prior Art] Ultrasonic probes are mainly composed of piezoelectric vibrators and transmit and receive ultrasonic waves, and are used as medical diagnostic equipment for inspecting the inside of the human body and for flaw detection inside metal welds. Used in ultrasonic inspection equipment such as ultrasonic flaw detection equipment.

[0003] Piezoelectric ceramic materials such as PZT and lead titanate are mainly used for piezoelectric vibrators in ultrasound probes, but recently composite piezoelectric materials made of piezoelectric ceramic and resin have also begun to be used. There is. This composite piezoelectric material has an electromechanical coupling coefficient equal to or higher than that of ordinary piezoelectric ceramic materials, and can lower the acoustic impedance of the vibrator, so it has a wider frequency band and pulse width than piezoelectric ceramic materials. It has the advantage of being able to generate narrow and good ultrasonic pulses.

On the other hand, due to its structure, composite piezoelectric materials have lower capacitance and higher electrical impedance than ordinary piezoelectric ceramic materials, so they are difficult to use when coaxially connecting the ultrasonic probe and the main body of the ultrasonic inspection device. The drawback is that the voltage loss in the receiving system increases due to the capacitance of the cable, and the sensitivity decreases. This tendency becomes more pronounced as the acoustic impedance is reduced in order to bring out the characteristics of the composite piezoelectric material.

[0005] In order to bring the capacitance of a composite piezoelectric body closer to that of a normal piezoelectric ceramic material, it is sufficient to reduce the proportion of the resin material portion in the piezoelectric body. In that case, specifically, the width of the resin material part between the piezoelectric ceramic material parts in the composite piezoelectric body is narrowed, or the interval between the resin material parts is widened, so the width of the piezoelectric ceramic material part becomes wider. , unnecessary resonance increases and manufacturing becomes difficult.

[0006] Furthermore, in array-type ultrasound probes that perform electronic focusing, there is a trend toward multi-elements for higher resolution, and as a result, the ultrasound transmission/reception area per piezoelectric transducer element has decreased. However, the electrical impedance of each element increases. Therefore, when a composite piezoelectric material is used, the increase in voltage loss becomes more significant.

[0007]

[Problems to be Solved by the Invention] As mentioned above, when a composite piezoelectric material is used for a piezoelectric vibrator in order to widen the bandwidth and improve resolution of an ultrasonic probe, when a normal piezoelectric ceramic material is used, In comparison, the capacitance is small and the electrical impedance is increased, so there is a problem that the voltage loss in the receiving system increases and the sensitivity decreases. An object of the present invention is to provide an ultrasonic probe that can achieve a wide band and high resolution without reducing sensitivity while using a composite piezoelectric material.

[0008]

[Means for Solving the Problems] In order to solve the above-mentioned problems, the present invention has a piezoelectric vibrator including a composite piezoelectric layer made of a piezoelectric ceramic material and a resin material, and has one surface of the piezoelectric vibrator. An ultrasonic probe having an ultrasonic wave transmitting/receiving surface is characterized in that the acoustic impedance on the ultrasonic wave transmitting/receiving surface side of the piezoelectric vibrator is smaller than that on the side opposite to the ultrasonic wave transmitting/receiving surface (backing material side).

[0009] Such an ultrasound probe has, for example, a piezoelectric vibrator having a laminated structure of a composite piezoelectric layer with low acoustic impedance and a piezoelectric ceramic layer with high acoustic impedance, and the composite piezoelectric layer is used as an ultrasonic wave transmitting/receiving surface. This is achieved by placing the piezoelectric ceramic layer on the backing material side, respectively. Another method is to change the proportion of the resin material part in the composite piezoelectric layer used in the piezoelectric vibrator in the thickness direction, increasing the proportion of the resin material part on the ultrasonic wave transmitting/receiving surface side, and increasing the proportion of the resin material part on the ultrasonic wave transmission/reception side. You may try to reduce it.

0010

[Operation] Since the piezoelectric vibrator of the present invention has a small acoustic impedance on the ultrasonic wave transmitting/receiving surface side, the characteristics of the transmitted ultrasonic wave as a whole are close to those of a composite piezoelectric material, and the ultrasonic wave with a wide band and narrow pulse width is transmitted. can get.

Furthermore, in the piezoelectric vibrator of the present invention, a piezoelectric ceramic layer having a large acoustic impedance or a composite piezoelectric layer having a large proportion of piezoelectric ceramic material can be disposed on the backing material side. The capacitance is larger than that of a normal single layer composite piezoelectric material layer in which the ratio of part to resin material part is uniform in the thickness direction, and the capacitance is not very small compared to the capacitance of a piezoelectric vibrator made of only a piezoelectric ceramic layer. Therefore, the electrical impedance of the piezoelectric vibrator is also equivalent to that of a normal single layer piezoelectric ceramic layer.

Therefore, the ultrasonic probe of the present invention can generate ultrasonic pulses with a broader band and narrower pulse width while ensuring sensitivity equivalent to that of a normal piezoelectric ceramic single-layer piezoelectric vibrator.

[0013]

Embodiments Hereinafter, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of an ultrasonic probe according to an embodiment of the present invention, and FIG. 2 is a sectional view taken along line A-A in FIG. 1.

In the ultrasonic probe shown in FIGS. 1 and 2, a piezoelectric ceramic layer 13 is provided on a backing material 11 with an electrode layer 12 interposed therebetween, and a composite piezoelectric layer 14 and an electrode layer 15 are provided thereon.
It has a structure of a laminated piezoelectric vibrator configured by laminating an acoustic matching layer 18 and an acoustic matching layer 18. The piezoelectric ceramic layer 13 is
Consists only of piezoelectric ceramic material. The composite piezoelectric layer 14 consists of a piezoelectric ceramic material portion 16 and a resin material portion 17,
In this example, it is composed of a 1-3 type composite piezoelectric layer.

That is, the piezoelectric vibrator of the ultrasonic probe in this embodiment has a composite piezoelectric layer 14 on the ultrasonic wave transmitting/receiving surface side (acoustic matching layer 18 side), and its acoustic impedance is equal to that of the ultrasonic wave transmitting/receiving surface. Opposite side (backing material 11
The acoustic impedance is smaller than the acoustic impedance of the piezoelectric ceramic layer 13 located on the side).

[0016] Such an ultrasonic probe is manufactured, for example, by the following steps. First, a piezoelectric vibrator made of a single PZT-based piezoelectric ceramic layer is prepared, and a portion of the vibrator in the thickness direction is two-dimensionally diced to a predetermined depth using a diamond blade. The grooves formed by this dicing are filled with epoxy resin and cured. Next, after flattening the surface, an electrode layer is formed by a method such as sputtering,
Further, by forming an acoustic matching layer, an ultrasonic probe as shown in FIGS. 1 and 2 can be obtained. In this case, the piezoelectric ceramic layer 13 and the piezoelectric ceramic material portion 16 in the composite piezoelectric layer 14 are integrally formed of one piezoelectric ceramic material.

Note that this embodiment shows an array type ultrasonic probe in which a large number of piezoelectric vibrators are linearly arranged.
Each vibrator is separated by grooves 19, and these grooves 19 are filled with resin.

The electrode layers 12 and 15 are connected to the main body of an ultrasonic testing apparatus (not shown) via a cable led out of the ultrasonic probe. A driving voltage is applied in series to the piezoelectric ceramic layer 13 and the composite piezoelectric layer 14 via the electrode layers 12 and 15 from a transmission circuit within the main body of the ultrasonic inspection apparatus.

In this case, the capacitance C0 in the thickness direction of the piezoelectric vibrator composed of the electrode layers 12 and 15, the piezoelectric ceramic layer 13, and the composite piezoelectric layer 14 is
The capacitance C1 of the composite piezoelectric layer 14 and the capacitance C2 of the composite piezoelectric layer 14
It is the series combined capacitance with and is expressed by the following formula. C0 = C1 ・C2 / (C1 + C2
) (1) Generally, the capacitance C is C=ε・s/t

(2) ε: relative dielectric constant s: area of dielectric layer t: thickness of dielectric layer

Therefore, if the thickness of the composite piezoelectric layer 14 is an appropriate value, the capacitance of the entire laminated piezoelectric vibrator will be equal to that of the piezoelectric ceramic unless the dielectric constant of the composite piezoelectric layer 14 is made extremely small. It does not become extremely small compared to the case of a single layer. This suppresses an increase in electrical impedance due to the use of the composite piezoelectric layer 14, and prevents a decrease in sensitivity due to voltage loss in the receiving system.

Furthermore, when the thickness of the composite piezoelectric layer 14 is set to about one-third or more of the thickness of the entire piezoelectric vibrator, the apparent acoustic impedance seen from the acoustic matching layer 18 side is It approaches that of the piezoelectric layer 14. Therefore, using the composite piezoelectric layer 14 makes it possible to widen the band.

FIG. 3 is a sectional view of an ultrasonic probe according to another embodiment of the present invention. In this embodiment, the composite piezoelectric layer 14 has a multilayer structure. That is, the composite piezoelectric layer 14 has a three-layer structure in the illustrated example, and the layer closer to the acoustic matching layer 18 side has a larger proportion of the resin material portion 17. Therefore, the composite piezoelectric layer 14 is the acoustic matching layer 1
The acoustic impedance is smaller toward the 8th side. An ultrasonic probe having such a structure can be easily manufactured by changing the thickness and cutting depth of the diamond blade used to dice the piezoelectric vibrator.

In this embodiment, as in the previous embodiment, the capacitance of the entire piezoelectric vibrator is larger than that of a piezoelectric vibrator composed of a single layer of a normal composite piezoelectric material.
It is possible to suppress an increase in electrical impedance and prevent a decrease in sensitivity, and it is also possible to achieve a wider band than in the case of a single piezoelectric ceramic layer.

FIG. 4 is a sectional view of an ultrasonic probe according to yet another embodiment of the present invention. In this embodiment, unlike the embodiment shown in FIG.
By changing the ratio of 7 continuously in the thickness direction, the acoustic impedance is made smaller toward the acoustic matching layer 18 side. Such a composite piezoelectric layer 14 can be realized by forming the grooves formed in the piezoelectric ceramic material portion 16 into a wedge shape. In order to form grooves having such a shape, the shape of the diamond blade used for dicing the piezoelectric vibrator may be wedge-shaped. It goes without saying that this embodiment also provides the same effects as the embodiment of FIG. 3.

[0025]

[Effects of the Invention] In the ultrasonic probe according to the present invention, the acoustic impedance on the ultrasonic wave transmitting/receiving surface side of the piezoelectric vibrator including the composite piezoelectric layer made of a piezoelectric ceramic material and a resin material is adjusted to the side opposite to the ultrasonic wave transmitting/receiving surface. By making the acoustic impedance smaller than that of the backing material, the characteristics of the transmitted ultrasonic wave as a whole are made close to those of the composite piezoelectric material,
It is possible to transmit broadband ultrasonic waves with narrow pulse widths.

Furthermore, by arranging a piezoelectric ceramic layer with a large acoustic impedance or a composite piezoelectric layer having a large proportion of piezoelectric ceramic material parts on the backing material side, the capacitance of the piezoelectric vibrator can be reduced by combining the piezoelectric ceramic material part and the resin material part. The capacitance of the piezoelectric vibrator is larger than that of a normal single-layer composite piezoelectric layer, which is uniform in the thickness direction, and the capacitance can be close to that of a piezoelectric vibrator made of only a piezoelectric ceramic layer. The physical impedance is also equivalent to that of a normal single layer piezoelectric ceramic layer. Therefore, the voltage loss in the receiving system is smaller than that of a normal single-layer composite piezoelectric layer vibrator, and the same pulse echo sensitivity as a normal piezoelectric ceramic single-layer piezoelectric vibrator can be obtained.

That is, according to the present invention, it is possible to transmit ultrasonic pulses with a wider band and narrower pulse width while maintaining the same level of sensitivity as that using a normal piezoelectric ceramic single-layer piezoelectric vibrator. Can be done.

[Brief explanation of the drawing]

[Fig. 1] A perspective view of an ultrasound probe according to an embodiment of the present invention.

[Figure 2] Cross-sectional view of the ultrasound probe in Figure 1 along line A-A

[Fig. 3] Cross-sectional view of an ultrasound probe according to another embodiment of the present invention

FIG. 4 is a sectional view of an ultrasound probe according to yet another embodiment of the present invention.

[Explanation of symbols]

11...Backing material
12... Electrode layer 13... Piezoelectric ceramic layer
14... Composite piezoelectric layer 15... Electrode layer
16...Piezoelectric ceramic material section 17...Resin material section
18...Acoustic matching layer

Claims (1)

[Claims] 1. An ultrasonic probe having a piezoelectric vibrator including a composite piezoelectric layer made of a piezoelectric ceramic material and a resin material, and in which one surface of the piezoelectric vibrator serves as an ultrasonic wave transmission/reception surface. The piezoelectric transducer is an ultrasonic probe characterized in that the acoustic impedance on the side of the ultrasonic wave transmitting/receiving surface is smaller than that on the side opposite to the ultrasonic wave transmitting/receiving surface.