JP2007175330A - Ultrasonic probe - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic probe having an acoustic matching layer capable of eliminating wasteful use of tungsten, or the natural resources, and freely controlling acoustic impedance. <P>SOLUTION: This ultrasonic probe is formed by having the acoustic matching layer formed by mixing metal powder on a resin matrix, on the radiation surface of a piezoelectric element, and the metal power is defined as cemented carbide mainly composed of tungsten carbide. These are formed of a waste material of antifriction and shock-resistant components. This constitution can freely control the acoustic impedance and effectively use the natural resources without any waste. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an ultrasonic probe in which metal powder is mixed in a resin matrix of an acoustic matching layer, and more particularly to an ultrasonic probe in which the metal powder is tungsten carbide.

(Background of the Invention)
The ultrasonic probe is applied as an ultrasonic wave transmission / reception unit of an ultrasonic diagnostic apparatus for medical use or the like, and detects a diseased part or the like by a reflected wave from the inside of a living body. Normally, an acoustic matching layer is provided on the transmission / reception surface of the ultrasonic probe to prevent ultrasonic propagation loss. One of these is an acoustic matching layer in which metal powder is mixed in a resin matrix.

(Example of conventional technology)
FIG. 1 is a cross-sectional view in the minor axis direction of an ultrasonic probe for explaining one conventional example. The ultrasonic probe is formed by, for example, fixing a piezoelectric element 1 made of PZT on a backing material 2 and providing an acoustic matching layer 3 on the wave transmitting / receiving surface side. The piezoelectric element 1 has a drive electrode 4 (ab) on both main surfaces, is formed in a strip shape, and a plurality of the piezoelectric elements 1 are arranged so that the width direction coincides with the major axis direction. Fillers are buried between the piezoelectric elements 1.

  The acoustic matching layer 3 is, for example, two layers. For example, both the first layer 3a and the second layer 3b can be obtained by mixing metal powder into an epoxy resin matrix. The metal powder is generally made of tungsten (W) with a high specific gravity. Then, the content of the metal powder is varied, the acoustic impedance of the first layer 3a is set to 8-9 M Rayl, the second layer 3b is set to 2 to 3 M Rayl, and sequentially reduced from the piezoelectric element 1 toward a living body (not shown). Thereby, the propagation loss of ultrasonic waves is prevented and the sensitivity is increased.

  The acoustic impedance of the piezoelectric element 1 here is 32M Rayl, and the living body is 1.5M Rayl. The first layer 3a and the second layer 3b of the acoustic matching layer 3 have a thickness of λ / 4 of the ultrasonic frequency. Normally, an acoustic lens (not shown) having a curvature in the minor axis direction is provided on the acoustic matching layer 2.

In such a case, since the first layer 3a and the second layer 3b of the acoustic matching layer 3 are formed by mixing metal powder into the resin matrix, the acoustic impedance can be freely controlled. Therefore, the acoustic impedance can be set to an optimum value and the propagation efficiency can be increased as compared with, for example, the case of using only glass or resin.
Japanese Patent Laid-Open No. 11-113908 Hokkaido Industrial Technology Information VOL.25 No.4 (Technology for Effective Use of Waste Cemented Carbide)

(Problems of conventional technology)
However, in the ultrasonic probe having the above-described configuration, the acoustic matching layer 3 is formed by mixing the metal powder into the resin matrix, so that a metal powder having a large specific gravity is required. That is, since the acoustic impedance of the resin matrix itself has a value of about 2 M Ray, for example, a metal powder having a large specific gravity is required.

  In particular, since the first layer 3a of the acoustic matching layer 3 is brought close to the acoustic impedance of the piezoelectric element 1, the content thereof is increased. For this reason, tungsten having a large specific gravity is selected as described above, but high specific gravity metals including this are expensive, and there is a concern that tungsten is particularly depleted.

(Object of invention)
It is an object of the present invention to provide an ultrasonic probe having an acoustic matching layer that can eliminate the waste of tungsten, which is a natural resource, and can freely control acoustic impedance.

(Points of interest)
The present invention pays attention to the effective utilization technique of the cemented carbide waste material disclosed in Non-Patent Document 1. That is, attention was focused on tungsten carbide, which is a cemented carbide used in parts for wear and impact resistance, including cutting tools.

(Solution)
As shown in the claims (Claim 1), in the ultrasonic probe in which an acoustic matching layer in which metal powder is mixed in a resin matrix is provided on the radiation surface of the piezoelectric element, the metal powder contains tungsten carbide. It is set as the structure which is the cemented carbide which made the main component.

  With such a configuration, the cemented carbide containing tungsten carbide as a main component has a specific gravity of about 14.5 and is substantially equal to tungsten (19), so that it can be sufficiently applied as a metal powder having a high specific gravity. And, as specified in claim 2, these are formed from, for example, scrap materials of parts for wear resistance and impact resistance, so that they can be used effectively without wasting natural resources.

  Hereinafter, an embodiment of the present invention will be described with reference to FIG. In addition, description of the same part as a prior art example is simplified or abbreviate | omitted.

  In the ultrasonic probe, as described above, the piezoelectric element 1 having the drive electrodes 4 (ab) on both principal surfaces is fixed to the backing material 2, and an acoustic matching layer having a two-layer structure is formed on the transmission / reception surface. Here, the first layer 3a of the acoustic matching layer is formed by mixing a metal powder made of cemented carbide into an epoxy resin matrix. The cemented carbide is made of waste materials such as wear and shock resistant parts such as cutting tools.

  The cemented carbide is mainly composed of tungsten carbide and added with additives such as cobalt. Tungsten carbide has a specific gravity of 16, and by adding cobalt, the specific gravity of the cemented carbide becomes approximately 14.5.

  For example, a molten resin mixed with metal powder and stirred and dispersed is applied onto the piezoelectric element 1 and polished to a thickness of λ / 4 (so-called coating). Or it forms in a sheet form previously and sticks with an adhesive agent. The second layer 3b of the acoustic matching layer is formed by, for example, a resin having a lower acoustic impedance than that of the first layer, for example, by a similar coating or sticking.

  With such a configuration, since the cemented carbide containing tungsten carbide as a main component is used as the metal powder, the specific gravity is the same as when tungsten is used. Therefore, the acoustic impedance can be freely controlled by mixing the metal powder into the resin matrix. In addition, the cemented carbide can be used effectively without wasting natural resources because it can use scraps of parts for wear resistance and impact resistance.

(Other matters)
In the above embodiment, the second layer 3b of the acoustic matching layer 3 is made of resin. However, as in the first layer 3a, a resin base material mixed with a cemented carbide or glass may be selected arbitrarily. Moreover, although the acoustic matching layer 3 is two layers, it may be a single layer or three or more layers. In these cases, when the acoustic matching layer 3 is made of a cemented carbide layer, the acoustic impedance can be selected as an optimal value between the piezoelectric element 1 and the living body, so that the propagation efficiency can be increased by minimizing the number of layers.

  For example, in the case of three layers, the acoustic impedance of the first layer 3a made of cemented carbide can be made larger than that of glass, resin, or the like, so that the acoustic impedance of the piezoelectric element 1 can be approached. Therefore, if a second layer and a third layer are provided on this, the propagation loss can be further reduced. Further, although the arrangement type in which a plurality of piezoelectric elements 1 are arranged in the major axis direction is used, it is needless to say that a single type including a Doppler type division plate can also be applied.

It is a figure of an ultrasonic probe explaining the present invention and one conventional example, the figure (a) is a front sectional view and the figure (b) is a sectional side view.

Explanation of symbols

  1 Piezoelectric element, 2 backing material, 3 acoustic matching layer, 4 drive electrode.

Claims (2)

  An ultrasonic probe comprising an acoustic matching layer in which a metal powder is mixed in a resin matrix on a radiation surface of a piezoelectric element, wherein the metal powder is a cemented carbide mainly composed of tungsten carbide. Sonic probe.   The ultrasonic probe according to claim 1, wherein the metal powder is made of a waste material for wear resistance or impact resistance.

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