JPH08223694A - Piezoelectric vibrator - Google Patents

Abstract

PURPOSE: To attain both high rigidity and a high electromechanical coupling coefficient by filling the space between two adjacent columnar piezoelectric substances with a packed bed and forming a lamination layer of hard and soft high polymer materials for the packed bed. CONSTITUTION: Plural piezoelectric substances 1 made of such piezoelectric materials as piezoelectric ceramics, etc., are arrayed in a matrix form. Then the space between two adjacent bodies 1 is filled with a packed bed 4 and these bodies 1 and beds 4 are formed into a single member as a whole. Every bed 4 has a 3-lamination structure where a soft polymer material 6 is held between the hard polymer materials 5 and 7, so that a piezoelectric vibrator 10 is hard on its surface part and soft at the part near the center of every substance 1. The materials 5 and 7 use the epoxy materials, etc., having Shore hardness of D50 or higher at an ordinary temperature, so that the vibrator 10 is not curved by its self-weight even when the vibrator 10 is supported in an overhung way. Then the material 6 uses an epoxy material, a urethane material, etc., having Shore hardness of not more than A40 at an ordinary temperature, so that the disturbance of mechanical vibrations can be reduced.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric vibrator mounted on the tip of a probe of an ultrasonic diagnostic apparatus or ultrasonic flaw detector.

[0002]

2. Description of the Related Art A piezoelectric vibrator is one in which piezoelectric bodies that reversibly convert electric signals and mechanical vibrations are arranged, and common electrodes are attached to the front and back surfaces. Piezoelectric ceramics, piezoelectric crystals, or the like are used as the material of the piezoelectric body. The performance of the piezoelectric vibrator is evaluated by the electromechanical coupling coefficient. This is a parameter that represents the conversion efficiency from mechanical vibration to electric signal and from electric signal to mechanical vibration, and is an important factor that influences the sensitivity of the ultrasonic probe. The electromechanical coupling coefficient depends on the piezoelectric material and its shape.

FIG. 6 shows the structure of a conventional piezoelectric vibrator.
In the conventional piezoelectric body, when the same piezoelectric material is used, the columnar shape often exhibits a better electromechanical coupling coefficient than the plate-like shape. Therefore, the piezoelectric vibrator is not formed by a single plate, but a plurality of columnar piezoelectric bodies 1 are arranged in a matrix form as shown in FIG.
To form a plate shape as a whole, and electrically connect with a common electrode for each row, and
A so-called composite piezoelectric body that operates as two piezoelectric bodies has been developed.

[0004]

The above-mentioned composite type piezoelectric vibrator theoretically realizes the electromechanical coupling coefficient of the columnar piezoelectric body 1. However, in actuality, the mechanical movement is hindered by the influence of the filling layer 2 of the rigid polymer material filled between the columnar piezoelectric bodies, so that the electromechanical coupling coefficient is greater than the electromechanical coupling coefficient of the columnar piezoelectric body 1. Substantially smaller. For example, when one piezoelectric body is formed by one plate, there is a piezoelectric material having an electromechanical coupling coefficient of about 50%. A single piezoelectric body 1 formed of the same material in a column shape
An electromechanical coupling coefficient of about 5% is shown. The composite type piezoelectric vibrator in which the pillar-shaped piezoelectric bodies 1 are assembled is
An electromechanical coupling coefficient of about 60% is shown when a hard polymer material having a hardness of about 0 is used, but an electromechanical coupling coefficient of 70% or more is obtained when a flexible soft polymer material of about 40 is used for Shore A. Show. Therefore, a high electromechanical coupling coefficient can be obtained if the filling layer is composed of a flexible soft polymer material, but the composite piezoelectric transducer has low rigidity and can be deformed by bending. Not only becomes more difficult and difficult to handle, but there is a possibility that the electrodes may peel off due to bending. It is an object of the present invention to provide a piezoelectric vibrator that can achieve both high rigidity and high electromechanical coupling coefficient.

[0005]

According to the present invention, in a piezoelectric vibrator in which a plurality of columnar piezoelectric bodies are arranged and a space between adjacent piezoelectric bodies is filled with a filling layer, the filling layer is a hard polymer. It is characterized by being a laminate of a material and a flexible polymer material.

[0006]

According to the present invention, since the adhesive layer has a laminated structure of a hard polymer material and a soft polymer material, it is possible to increase both rigidity and electromechanical coupling coefficient.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the piezoelectric vibrator according to the present invention will be described below with reference to the drawings. Piezoelectric vibrators are installed at the tip of the ultrasonic probe of ultrasonic diagnostic equipment, the source of therapeutic waves (ultrasonic probe) of ultrasonic calculus breaking equipment and ultrasonic thermotherapy equipment, and generate electrical signals and mechanical vibrations. It is for reversible conversion.

FIG. 1 shows the structure of a one-dimensional array type piezoelectric vibrator according to the first embodiment. The figure (a) is a top view and the figure (b) is an AA 'cross section figure of the figure (a). It should be noted that FIG. 1A shows the electrode, the acoustic matching layer and the backing material removed, and FIG. 1B shows the acoustic probe including the acoustic matching layer 11 and the backing material 12 mounted on the ultrasonic probe. ing.

The piezoelectric vibrator 10 according to this embodiment comprises a plurality of columnar piezoelectric bodies 1 made of a piezoelectric material such as piezoelectric ceramics.
Are arranged in a matrix. The columnar shape means a rod body having a rectangular cross section whose thickness is larger than its width. The cross-sectional shape may be any shape such as a polygonal shape, a circular shape, an elliptic shape or the like as long as it is longer than the area of the upper surface of FIG. The space between the adjacent piezoelectric bodies 1 is filled with the filling layer 4, and is formed as one member (one piezoelectric vibrator) as a whole. A predetermined number in the vicinity, for example, 1 for every 1 × 6 piezoelectric bodies 1 for one row
The two common electrodes 3 are commonly connected. The 1 × 6 piezoelectric bodies 1 commonly connected by the common electrode 3 constitute a so-called one composite piezoelectric body and correspond to one channel.

The filling layer 4 is formed from the front surface to the back surface of the columnar piezoelectric body 1. The filling layer 4 hardens the surface of the piezoelectric vibrator and softens the vicinity of the center of the piezoelectric body 1. Therefore, the soft polymer material 6 is sandwiched between the hard polymer materials 5 and 7 and has a three-layer structure. Is formed.

As the rigid polymer materials 5 and 7, when the piezoelectric vibrator 10 is supported in a cantilever manner, the piezoelectric vibrator 10 can maintain a plate shape without being deformed by its own weight such as bending and the like at room temperature (when cured). ), A filling material having a hardness of Shore D50 or more, such as an epoxy material, is used. As the soft polymer material 6, a filling material such as an epoxy material or a urethane material having a hardness of Shore A 40 or less at room temperature (during curing) is used so as to reduce interference with mechanical vibration of the piezoelectric body 1. Preferably. Further, in consideration of easiness of processing, as the rigid polymer materials 5 and 7, a plastic material which exhibits hardness at room temperature and flexibility at high temperature is used. Specifically, the rigid polymer materials 5 and 7 are resins having a glass transition temperature of about 80 degrees Celsius. By using this resin, since it has flexibility at 80 degrees or more, shape processing such as giving a curvature can be easily performed, and sufficient rigidity can be obtained to maintain the piezoelectric vibrator 10 by obtaining necessary hardness at room temperature. Can be earned.

From the viewpoint of increasing the electromechanical coupling coefficient of the piezoelectric vibrator 10, the hard polymer materials 5 and 7 are used.
It is preferable that the total thickness of the flexible polymer material 6 is thin and the thickness of the flexible polymer material 6 is large. On the other hand, from the viewpoint of increasing the rigidity of the piezoelectric vibrator 10, it is preferable to increase the total thickness of the hard polymer materials 5 and 7 and reduce the thickness of the soft polymer material 6. Thus, the rigidity and the electromechanical coupling coefficient have a property of not accepting each other. When the material of Shore D50 is used as the hard polymer materials 5 and 7, and the material of Shore A40 is used as the soft polymer material 6, rigidity sufficient to maintain the plate shape of the piezoelectric vibrator 10 is obtained. In order to achieve this, the thickness of each of the hard polymer materials 5 and 7 is D / 3 or less than D / 3 with respect to the thickness D of the piezoelectric body 1 (the same as the total thickness of the filling layer 4), that is, the high hardness The total thickness of the molecular materials 5 and 7 is formed to be 2 · D / 3 or less than 2 · D / 3, and the remaining D / 3 or more than D / 3 is formed of the soft polymer material 6.

With such a structure, the following experimental results were obtained. Here, the piezoelectric body 1 was measured using piezoelectric ceramics. In the case of piezoelectric ceramics, the electromechanical coupling coefficient (Kt) is 51% if it is a single plate, and the electromechanical coupling coefficient (K33) is if it is a columnar single body.
Indicates 75%. When the conventional piezoelectric vibrator shown in FIG. 6 is constructed using this columnar piezoelectric ceramic, the electromechanical coupling coefficient of the piezoelectric vibrator is about 60%. On the other hand, in the piezoelectric vibrator 10 of this embodiment, an electromechanical coupling coefficient of 70% or more is obtained.

As described above, according to this embodiment, the filling layer 4 between the adjacent piezoelectric bodies 1 has a laminated structure of the hard polymer materials 5 and 7 and the soft polymer material 6, so that the piezoelectric vibration is generated. Even when the child 10 is supported in a cantilever manner, the piezoelectric vibrator 10 has rigidity enough to maintain a plate-like shape without being bent or deformed by its own weight, and a good electromechanical coupling coefficient can be obtained.

Next, a second embodiment will be described. FIG. 3 shows a perspective structure of a piezoelectric vibrator according to the second embodiment. FIG.
3A is a sectional view taken along line 4A-4A ′ in FIG. 3, and FIG. 4B is a sectional view taken along line 4B-4B ′ in FIG. The same parts as those in FIG. 1 are designated by the same reference numerals.

Also in this embodiment, the piezoelectric bodies 1 are arranged in a matrix as in the first embodiment. Piezoelectric bodies 1 adjacent to each other along the first direction (for example, the row direction, the left-right direction on the paper surface in FIG. 3)
The first filling layer 8 filling the space and the second filling layer 9 filling the space between the piezoelectric bodies 1 adjacent to each other along the second direction (eg, the column direction) intersecting (orthogonal to) the first direction. The soft polymer material 6 and the hard polymer material 7 have a two-layer structure, and the hard polymer material 5 and the soft polymer material 6 have a two-layer structure.

The first filling layer 8 is formed by laminating the soft polymer material 6 and the hard polymer material 7 in this order from the surface side. The thickness of the hard polymer material 7 is set to the thickness of the piezoelectric body 1 (filling layer 4
(The same as the overall thickness of D), D / 3 or less than D / 3, and the remaining 2 · D / 3 or more than 2 · D / 3 is formed of the soft polymer material 6.

The second filling layer 9 is formed by laminating the hard polymer material 5 and the soft polymer material 6 in this order from the surface side. The thickness of the hard polymer material 5 is D / 3 or less than D / 3, and the remaining 2 · D / 3 or more than 2 · D / 3 is formed of the soft polymer material 6.

With this structure, the piezoelectric bodies 1 and the hard polymer material 7 are alternately arranged in the first direction, and both of them form a line-shaped high hardness layer along the first direction. Thus, the required rigidity can be obtained in the first direction. Further, the piezoelectric bodies 1 and the hard polymer material 5 are alternately arranged in the second direction, and a linear high hardness layer is formed along the first direction in both, so that the rigidity required in the second direction is increased. can get. Therefore, as a whole, the rigidity required for the curvature in all directions is obtained. Moreover, since the proportion of the soft polymer material 6 is larger than that in the first embodiment, the electromechanical coupling coefficient can be increased.

The present invention is not limited to the above-mentioned embodiments, but can be modified in various ways. The piezoelectric vibrator of the above-described embodiment can be applied to various purposes by changing its plane shape, electrode shape, and arrangement of electrodes. For example,
The one-dimensional array type probe that is widely used in the linear type and the sector type of the ultrasonic diagnostic apparatus has a planar rectangular shape on the front and back surfaces of a piezoelectric vibrator in which piezoelectric bodies are arranged in a matrix so as to form a planar rectangular shape as a whole. This is completed by arranging a plurality of electrodes in one dimension. A two-dimensional array type probe that will be put to practical use in the future has a plurality of planar rectangular electrodes arranged in a two-dimensional matrix on the front and back surfaces of a piezoelectric vibrator in which piezoelectric bodies are arranged in a matrix so that the entire surface becomes a rectangular shape. Completed by arranging in. Further, in the case of an annular-type ultrasonic wave generation source (ultrasonic probe) used in the ultrasonic flaw detector as shown in FIG. 5, the piezoelectric bodies 1 are arranged in a matrix so as to be substantially circular as a whole. This is completed by arranging a plurality of concentric ring-shaped electrodes 31 to 35 on the front and back surfaces of the piezoelectric vibrator array.

[0021]

According to the present invention, in a piezoelectric vibrator in which a plurality of columnar piezoelectric bodies are arranged and the space between the adjacent piezoelectric bodies is filled with a filling layer, the filling layer is made of a hard polymer material and a soft material. Since it is characterized by being laminated with a polymer material, it is possible to enhance rigidity, ensure ease of handling, and approximate the electromechanical coupling coefficient to that of a columnar piezoelectric body. it can.

[Brief description of drawings]

FIG. 1 is a configuration diagram of a piezoelectric vibrator according to a first embodiment.

FIG. 2 is a structural diagram of a piezoelectric vibrator for one channel.

FIG. 3 is a structural diagram of a piezoelectric vibrator for one channel according to a second embodiment.

4 is a sectional view of the piezoelectric vibrator of FIG.

FIG. 5 is a diagram showing an application example of the piezoelectric vibrator according to the present invention to an annular type.

FIG. 6 is a structural diagram of a conventional piezoelectric vibrator for one channel.

[Explanation of symbols]

1 ... Piezoelectric body, 2, 4, 8, 9 ... Filled layer,
3 ... Electrode, 5, 7 ... Hard polymer material, 6 ... Soft polymer material, 10 ... Piezoelectric vibrator, 1
1 ... Acoustic matching layer, 12 ... Backing material.

Claims (6)

[Claims] 1. A piezoelectric vibrator in which a plurality of columnar piezoelectric bodies are arranged and a space between adjacent piezoelectric bodies is filled with a filling layer, wherein the filling layer is made of a hard polymer material and a soft polymer material. A piezoelectric vibrator, wherein the piezoelectric vibrator is formed by stacking. 2. The piezoelectric vibrator according to claim 1, wherein the rigid polymer material exhibits hardness at room temperature and exhibits flexibility at high temperature. 3. The piezoelectric vibrator according to claim 1, wherein the filling layer has a three-layer structure in which the soft polymer material is sandwiched between the hard polymer materials. 4. The piezoelectric vibrator according to claim 1, wherein a common electrode is connected to the plurality of piezoelectric bodies. 5. The hard polymer material is formed to a thickness of one third or less of the thickness of the piezoelectric body, and the soft polymer material is formed to a thickness of two thirds or more of the thickness of the piezoelectric body. The piezoelectric vibrator according to claim 1, wherein the piezoelectric vibrator is formed. 6. The piezoelectric body is arranged two-dimensionally,
A first filling layer for filling the space between the piezoelectric bodies adjacent to each other along the direction has a two-layer structure in which the soft polymer material and the hard polymer material are laminated in this order from the surface, and intersects in the first direction. The second filling layer filling the space between the piezoelectric bodies adjacent to each other along the second direction has a two-layer structure in which the hard polymer material and the soft polymer material are laminated in this order from the surface. The piezoelectric vibrator according to claim 1.