JP4291501B2 - Broadband transducer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a broadband transmitter / receiver suitable for use in the ocean such as fish school detection and depth measurement in the ocean, and is particularly configured by arranging a plurality of electroacoustic transducers using piezoelectric vibrators. The present invention relates to an element array type broadband transducer.
[0002]
[Prior art]
Conventional ocean transmitters and receivers have proposed technologies such as shortening the wavelength of underwater acoustic waves by increasing the frequency used, or increasing the bandwidth to improve signal response, in order to improve acoustic measurement accuracy. I came. In particular, for broadband technology, considerable results have been obtained through the use of matching layers.
[0003]
In general, the matching layer used in the electroacoustic transducer of the transducer is focused on the acoustic impedance density of the matching layer material, and the acoustic wave in the piezoelectric transducer and the underwater ultrasonic transducer that converts electrical signals and acoustic signals. Various materials were selected from the target of the geometric mean value of the acoustic impedance density of water as a propagation medium. The length dimension of the matching layer is set to ¼ of the sound wave propagation wavelength λ in the matching layer at the operating frequency of the piezoelectric vibrator. It was attached so that the length direction matched.
[0004]
As shown in FIG. 6A, an electroacoustic transducer in which one matching layer 2a is provided on the acoustic radiation surface of one piezoelectric vibrator 1a is used to increase the bandwidth of the transmitter / receiver using the matching layer. The basic structure is the structure to be performed. When the bandwidth obtained by providing one matching layer 2a is not sufficient, a second matching layer 2b or a third matching layer 2c is provided as shown in FIG. By adopting the configuration, it was intended to further broaden the bandwidth.
[0005]
Even in an element array type transducer as shown in FIG. 7A, a sufficient bandwidth can be obtained by arranging a plurality of electroacoustic transducer elements each having a matching layer 2d on the piezoelectric vibrator 1b. If not obtained, as in the case of the transducer shown in FIG. 6, a second matching layer 2e or a third matching layer 2f is provided to form a multiple matching layer as shown in FIG. 7B. It was common to deal with this.
[0006]
[Problems to be solved by the invention]
However, in the case of a structure in which a plurality of electroacoustic transducers provided with multiple matching layers are arranged as in the transducer shown in FIG. 7B, each electroacoustic transducer is bonded to one piezoelectric vibrator. Since it is formed by attaching two or more matching layers by the above method, it is necessary to prevent the matching layer from being displaced and to manage the thickness of the adhesive layer. As a result, there has been a problem that the variation in characteristics becomes conspicuous as the adhesive layer serving as a boundary between the piezoelectric vibrator and the matching layer increases.
[0007]
Further, materials having different acoustic impedance densities are used as the second and third matching layers, but the length dimension in the sound wave propagation direction of each matching layer is 1/4 of the sound wave propagation wavelength λ of each material. As a result, the length of the electroacoustic transducer having a single matching layer is increased, and as a result, the size of the transducer must be increased. There was also.
[0008]
Accordingly, an object of the present invention is to provide a structure of an electroacoustic transducer element called a multi-matching layer in contrast to the effect of widening the band obtained by providing a single matching layer in a conventional element array type wide-band transducer. By using a combination of electroacoustic transducers with a basic configuration with a single matching layer without the need for complication or increase in length, a broadband transmitter / receiver that achieves wider bandwidth can be obtained. Is to provide.
[0009]
[Means for Solving the Problems]
The broadband transducer according to the present invention is an element array type underwater ultrasonic transducer configured by arranging a plurality of electroacoustic transducers each having a single matching layer on a piezoelectric vibrator. As a combination of two or more types of matching layers obtained from materials having velocity anisotropy with different sound wave propagation speeds depending on the direction in which the sound waves propagate through the material, and a plurality of matching layer lengths in the sound wave propagation direction are used. Is a broadband transmitter / receiver unified with a length determined by the characteristic value of the matching layer whose sound wave propagation speed is faster than the median or the median.
[0010]
According to the broadband transducer of the present invention, by providing a plurality of types of matching layers having the same dimensions and different sound wave propagation speeds in the length direction, which is the sound wave propagation direction, to a piezoelectric vibrator of one specification, resonance characteristics are obtained. A plurality of electroacoustic transducers with different characteristics can be obtained, and by combining them to form an element array, a broadband transducer having sensitivity characteristics can be obtained by combining the characteristics of the electroacoustic transducer elements with different sensitivity characteristics. be able to.
[0011]
That is, the present invention relates to an element array type broadband transducer in which a plurality of electroacoustic transducers each provided with a single matching layer are arranged on a piezoelectric vibrator, and watertightness is provided by a method such as resin molding. The matching layer is used in combination of two or more types obtained from materials having velocity anisotropy with different sound wave propagation speeds depending on the direction in which sound waves propagate through the material, and the matching layer has a plurality of lengths in the sound wave propagation direction. In this matching layer, the sound wave propagation speed is the median value or a broadband transmitter / receiver that unifies with a length determined by the characteristic value of the matching layer that is faster than the median value.
[0012]
DETAILED DESCRIPTION OF THE INVENTION
The broadband transmitter / receiver of the present invention will be described below.
[0013]
FIG. 1 is an element array type broadband transducer according to an embodiment of the present invention, and is a cross-sectional view seen from the top and side showing the arrangement of two types of electroacoustic transducers. FIG. 1A shows a front view of a broadband transducer, and FIG. 1B shows a cross-sectional view taken along line AA in FIG.
[0014]
In the conventional configuration, as shown in FIG. 7, in the case of arranging a plurality of electroacoustic transducers having a single matching layer on a piezoelectric vibrator in an element array type transducer, the same material is used for one element. The electroacoustic transducers have the same characteristics because the matching layer having the dimensions of 1 is applied to each piezoelectric vibrator by bonding or the like.
[0015]
This is because, as shown in FIG. 6, the element arrangement type transducer is a directivity operation and the outer diameter size ratio of the transducer with respect to the transducer comprising the electroacoustic transducer element by one piezoelectric transducer. This is because, in order to achieve the avoidance of the generation of the coupling vibration caused by the above, it was configured as an initial purpose to replace a plurality of electroacoustic transducers having a shape obtained by subdividing the acoustic radiation surface with an array.
[0016]
That is, the conventional transmitter / receiver shown in FIG. 7 includes 16 subdivided electroacoustic transducers, each of which is composed of one electroacoustic transducer having an acoustic radiation surface shape as shown in FIG. Thus, it can be said that the acoustic radiation surface is reconfigured so that the shape and the outer diameter are equal.
[0017]
Here, since the 16 electroacoustic transducers have the same characteristics, the resonance characteristics of the transducers arranged in the element are the same as those of the transducer of one electroacoustic transducer in FIG. A single resonance at the operating frequency of the piezoelectric vibrator is changed to a double resonance characteristic having two primary and secondary resonance points by providing one matching layer, and a plurality of electroacoustic transducers are provided. Even if arranged, the resonance point does not increase further.
[0018]
On the other hand, in the broadband transducer according to the present invention, by using a plurality of matching layers having the same dimensions and different sound wave propagation velocities, a plurality of electroacoustic transducers in which the resonance points of the double resonance characteristics are shifted can be obtained. By combining these, a broadband transducer having three or more resonance points is configured.
[0019]
【Example】
A broadband transducer according to an embodiment of the present invention will be described below.
[0020]
In the broadband transducer according to the present invention, two types of matching layers having different characteristics are obtained from one type of material. The material having the anisotropy of the sound wave velocity used as the matching layer material is the glass cloth base epoxy resin laminate 22. This material has different sound wave propagation speeds in the direction along the glass cloth fiber as the base material and in the direction perpendicular to the fiber.
[0021]
Conventionally, when a glass cloth base epoxy resin laminate is used as a matching layer material, either the direction along the glass cloth fiber or the direction perpendicular to the fiber has been unified as the sound wave propagation direction as the matching layer. However, in this embodiment, the first matching layer 22a in which the direction along the fiber is the length direction that is the sound wave propagation direction of the matching layer is used, and the direction orthogonal to the fiber is the sound wave propagation direction of the matching layer. A second matching layer 22b having a certain length direction is used.
[0022]
Alternatively, in place of the first matching layer 22a or the second matching layer 22b, a third matching layer (in which a direction oblique to the direction along the fiber is used as the sound wave propagation direction of the matching layer ( It is also possible to process and use (not shown).
[0023]
In the glass cloth base epoxy resin laminate, as shown in FIG. 3, the sound wave propagation speed in the X and Y directions along the glass cloth fiber is 30% or more with respect to the sound wave propagation speed in the Z direction perpendicular to the glass cloth fiber. Since it shows a large value, two types of matching layers having the same density and different sound wave propagation speeds can be obtained. About the matching layer 22b which determines the length direction dimension L of the matching layer 22a with the characteristic value in the X or Y direction along the glass cloth fiber having a high sound wave propagation speed, and uses the Z direction orthogonal to the glass cloth fiber as the sound wave propagation direction. Is processed with L in the length direction.
[0024]
As a result, if the matching layer 22a whose direction along the fiber is the sound wave propagation direction is ¼ of the sound wave propagation wavelength λa in the matching layer at the operating frequency, the direction perpendicular to the fiber is The matching layer 22b having the sound wave propagation direction has a length that is substantially 30% or longer with respect to ¼ of the sound wave propagation wavelength λb in the matching layer at the use frequency.
[0025]
In the embodiment, two types of matching layers 22a and 22b manufactured from a glass cloth base epoxy resin laminated plate 22 are applied to a prismatic vibrator 21 that resonates at a frequency of 70 kHz in the length direction by bonding. Electroacoustic transducers 23a and 23b having matching layers are obtained.
[0026]
As the material properties of the glass cloth base epoxy resin laminate, the density ρ = 1.9 × 10 ³ (kg / cm ³ ), the sound wave propagation velocity Ca = 3150 (m / sec) along the fiber, Since the sound wave propagation velocity Cb in the orthogonal direction is 2340 (m / sec), the length of the matching layer 22a having the sound wave propagation direction in the direction along the fiber with respect to the use frequency of 70 kHz is ¼ of the wavelength λ. Is set to about L = 11.3 (mm), and the matching layer 22b having the direction perpendicular to the fiber as the sound wave propagation direction is also formed with this length.
[0027]
FIG. 4 shows an external view of electroacoustic transducers 23a and 23b configured by bonding two types of matching layers 22a and 22b to the piezoelectric vibrator 21 with a thermosetting epoxy resin adhesive. Both elements have the same dimensions. The graph shows the respective impedance characteristics. The characteristics of the electroacoustic transducer 23a are represented by the impedance frequency characteristics 24a, and the characteristics of the electroacoustic transducer 23b are represented by the impedance frequency characteristics 24b.
[0028]
Here, the electroacoustic transducer 23b bonded with the matching layer 22b whose direction perpendicular to the fiber is the sound wave propagation direction is bonded to the electroacoustic transducer 23a bonded with the matching layer 22a whose direction along the fiber is the sound wave propagation direction. On the other hand, the primary resonance point shifts to the low frequency side of about 8 kHz. When these electroacoustic transducers 23a and 23b are combined, a transducer having four resonance points in the resonance characteristics can be obtained.
[0029]
On the other hand, in the conventional transducer configuration with one type of matching layer, there are two resonance points. In the broadband transducer according to the embodiment of the present invention, each of the two types of electroacoustic transducer elements 23a and 23b is used to form a 4 × 4 element array, and between elements and around the element array. The cork 25 is bonded to position the element and sound is insulated from the surroundings. After the connection with the signal cable 26, the whole is molded with a polyurethane rubber mold 27 to provide watertightness, and the conventional transmission / reception shown in FIG. A broadband transmitter / receiver with the same dimensions as the wave generator was manufactured.
[0030]
FIG. 1 is an explanatory diagram of a broadband transducer according to this embodiment. The arrangement of the electroacoustic transducers 23a and 23b in this broadband transducer is such that they are alternately arranged as shown in FIG. The sensitivity characteristics of the broadband transducer thus obtained are as shown in the transmission sensitivity frequency characteristic 28 and the reception sensitivity frequency characteristic 30 of FIG. In FIG. 2, as a conventional example, the transmission sensitivity frequency characteristic 29 when only the matching layer 22a having the direction along the fiber used in this embodiment as the sound wave propagation direction is used in the transducer shown in FIG. The reception sensitivity frequency characteristic 31 is also shown.
[0031]
It can be seen that the bandwidth of the wideband transducer according to the embodiment of the present invention is broader than the sensitivity characteristics of the transducer obtained with the conventional configuration. This is because the resonance characteristics of the electroacoustic transducer 23b provided with the matching layer 22b shift to the low frequency side with respect to the resonance characteristics of the electroacoustic transducer 23a provided with the matching layer 22a, and the elements are arranged by mixing them. This is because, by superimposing the sensitivity characteristics of the two element groups that are out of band, the band is expanded toward the low frequency side, and the effect of suppressing the sensitivity change in the band is obtained.
[0032]
Multi-matching layers in conventional transducers are made by providing multiple matching layers to cause multiple resonances of the piezoelectric vibrator, continuously increasing the sensitivity characteristics near the resonance frequency, and changing the sensitivity within the band. However, in the wideband transducer of the present invention, a plurality of electrical conversion acoustic elements are divided into several groups, and the resonance characteristics of each element group are shifted. When these are combined to form an element array, one transducer can have multiple resonance frequencies, approximating the same effect as in the case of multiple resonance of a piezoelectric vibrator using multiple matching layers It is intended to be obtained.
[0033]
According to the wideband transducer of the present invention, complicated characteristic estimation calculation such as when a multiple matching layer is added to a piezoelectric vibrator is unnecessary, and multiple characteristic estimations when a single matching layer is added are performed. The sensitivity characteristics as a transducer after the element arrangement is performed from the combination of these characteristics can be estimated relatively easily.
[0034]
Further, since a plurality of matching layers can be obtained from one material, it is not necessary to investigate many selection layer materials and make selections and combinations.
[0035]
Furthermore, obtaining two or more matching layers from one material has other advantages. For example, when searching for a resin material having a sound wave propagation speed equal to the matching layers 22a and 22b obtained from the glass cloth base epoxy resin laminate used in the present embodiment, a general resin material has a high sound wave propagation speed. Since the density tends to increase, the density of the matching layer material having the sound wave propagation speed equivalent to the matching layer 22a is usually larger than the density of the matching layer material having the sound wave propagation speed equivalent to the matching layer 22b. It is.
[0036]
In this case, the deviation of resonance between the two types of electroacoustic transducers is smaller than the case where the density is the same in calculation. In addition, from the above tendency, it is very difficult to find a material with different resin materials having the same density and greatly different sound wave propagation speeds. Therefore, the advantage of obtaining a plurality of matching layers from one material is great both in terms of characteristics and availability of the matching layer material.
[0037]
By using the glass cloth base epoxy resin laminate as the matching layer in the above embodiment, and obtaining two types of matching layers from materials having anisotropy in sound wave propagation velocity, and using them in combination, the same matching layer Although it has been shown that the effect of broadening the bandwidth can be greatly obtained when only one type is used, the present invention does not prescribe only the glass cloth base epoxy resin laminate as the material of the matching layer, and is anisotropic in speed. The same effect can be obtained even with other materials having properties. However, the magnitude of the effect depends on the characteristics of the material used, and it is not guaranteed that the same effect as in this embodiment can be obtained as long as the material has anisotropy.
[0038]
In this example, the glass cloth base epoxy resin laminate was used as the material having the anisotropy of the sound wave propagation speed, but the material having the anisotropy of the sound wave propagation speed was an epoxy of the cloth base material or the paper base material. There are resin laminates, phenol resin laminates, etc., and many of the resins molded with glass fiber or carbon fiber oriented in a certain direction have anisotropy in the sound wave propagation speed. Such a material can also be used.
[0039]
In this example, the dimension was determined so that the length of the matching layer was 1/4 of the sound wave propagation wavelength λ with respect to the sound wave propagation speed in the fiber direction of the glass cloth base epoxy resin laminate. However, it is not always necessary to be 1/4 of the wavelength λ.
[0040]
In this example, the direction along the fiber of the glass cloth base material and the direction orthogonal to the fiber are used as the sound wave propagation direction in the matching layer, but the direction inclined from these orthogonal axes is matched as the sound wave propagation direction. If the layer is processed, it is also possible to obtain matching layers with different acoustic wave propagation velocities.
[0041]
【The invention's effect】
As described above, according to the present invention, the configuration using a matching layer is a transducer of a system in which electroacoustic transducers having a single matching layer, which is the simplest form, are arranged. In addition, a broadband transmitter / receiver having a wider bandwidth can be provided by a simple method in which matching layers having different material properties are obtained from a single material.
[Brief description of the drawings]
FIG. 1 is a diagram showing an element array type broadband transducer according to an embodiment of the present invention, and is a cross-sectional view seen from the top and side showing the arrangement of two types of electroacoustic transducers. 1A is a front view, and FIG. 1B is a cross-sectional view taken along line AA in FIG.
FIG. 2 is a graph showing sensitivity characteristics of an underwater ultrasonic transducer according to the present invention and an underwater ultrasonic transducer according to a conventional configuration. FIG. 2A shows the relationship between transmission power sensitivity and frequency, and FIG. 2B shows the relationship between reception power sensitivity and frequency.
FIG. 3 is a diagram showing a relationship between a sound wave propagation direction in a glass cloth base epoxy resin laminate and a sound wave propagation direction and a length direction of a matching layer obtained from the resin plate.
FIG. 4 is a diagram showing a relationship between fiber directions of glass cloth base epoxy resin laminates in matching layers of two types of electroacoustic transducers. FIG. 4A is a diagram showing an electroacoustic transducer having a matching layer in which the direction along the fiber and the sound wave propagation direction are aligned, and FIG. 4B shows the direction along the fiber as the sound wave propagation direction. The figure which shows the electroacoustic transducer which has the matching layer which makes a right angle, FIG.4 (c) is a figure which shows the impedance characteristic of each electroacoustic transducer.
FIG. 5 is a cross-sectional view of a conventional transducer using an electroacoustic transducer in which a single matching layer is provided on a single piezoelectric vibrator, as viewed from the top and side. 5A is a front view, and FIG. 5B is a BB cross-sectional view in FIG.
FIG. 6 is a cross-sectional view seen from the side of a conventional transducer using an electroacoustic transducer having a multi-matching layer by adding two matching layers.
FIG. 7 is a cross-sectional view seen from the top and side of a conventional element array type transducer in which a plurality of electroacoustic transducers each having a single matching layer provided on one piezoelectric vibrator are arrayed. Fig.7 (a) is a front view, FIG.7 (b) is CC sectional drawing in Fig.7 (a).
FIG. 8 is a cross-sectional view as seen from the side of a conventional transducer in which a plurality of electroacoustic transducer elements that are made into multiple matching layers by adding two matching layers are arranged.
FIG. 9 is a diagram showing a conventional transducer using an electroacoustic transducer in which one matching layer is provided in one piezoelectric vibrator. Sectional drawing seen from the upper surface and side surface of the transducer which made the structure with the same shape dimension of FIG. 8 and an acoustic radiation surface. 9A is a front view, and FIG. 9B is a CC cross-sectional view in FIG. 9A.
[Explanation of symbols]
1a, 1b, 21 Piezoelectric vibrators 2a-2f Matching layer 22 Glass cloth base epoxy resin laminates 22a, 22b Matching layers 23a, 23b Electroacoustic transducers 24a, 24b Impedance frequency characteristics 25 Cork 26 Signal cable 27 Polyurethane rubber mold 28 , 29 Transmission sensitivity frequency characteristics 30,31 Reception sensitivity frequency characteristics

Claims (1)

In an element array type broadband transducer in which a plurality of electroacoustic transducers each provided with a single matching layer on a piezoelectric vibrator are arranged and made watertight by a method such as resin molding, the matching layer is made of a material. Are used in combination of two or more materials obtained from materials with velocity anisotropy that have different sound wave propagation speeds depending on the direction of sound wave propagation, and the length of the sound wave propagation direction of the matching layer is propagated in multiple matching layers. A broadband transmitter / receiver characterized in that the speed is unified with a length determined by a characteristic value of a matching layer whose median or faster than the median.

Images