JP4291500B2 - Broadband transducer - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention is a broadband transmitter / receiver suitable for use in fish detection in the ocean and ocean detection at depth, and in particular, is 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]
Conventionally, for transducers in the field of fish detection in the ocean and ocean detection at depth, in order to improve acoustic measurement accuracy, shortening the wavelength of underwater acoustic waves by increasing the frequency used, or signal response Techniques such as wideband have been proposed to improve this. In particular, with regard to the technology for widening the bandwidth of the transmitter / receiver, considerable results have been achieved by using the matching layer.
[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. The material is selected from various materials with the target being the geometric mean value of the acoustic impedance density of each of the water as the propagation medium.
[0004]
The length dimension of the matching layer is set to 1/4 of the sound wave propagation wavelength λ in the matching layer at the use frequency of the piezoelectric vibrator, and the sound wave propagation direction and the matching layer are bonded to the acoustic radiation surface of the piezoelectric vibrator by a method such as adhesion. Are attached so that their length directions coincide.
[0005]
FIG. 5 is a cross-sectional view of a conventional transducer using an electroacoustic transducer in which a single matching layer is provided on one piezoelectric vibrator, as viewed from the top and side. FIG. 5 (a) is a front view of the transducer, and FIG. 5 (b) is a BB cross-sectional view in FIG. 5 (a).
[0006]
In widening the bandwidth of the transducer by improving the matching layer of the transducer, as shown in FIG. 5 (a), an electric circuit in which one matching layer 2a is provided on the acoustic radiation surface of one piezoelectric vibrator 1a. A configuration using an acoustic transducer is a basic form. If the bandwidth obtained by providing one matching layer 2a is not sufficient, a second matching layer 2b or a third matching layer 2c is newly provided as shown in FIG. By adopting a layer structure, a wider bandwidth was achieved.
[0007]
Further, in an element array type transducer as shown in FIG. 7, a sufficient bandwidth must be obtained by arranging a plurality of electroacoustic transducers each having a matching layer 2d on the piezoelectric vibrator 1b. For example, as in the case of the transducer shown in FIG. 7, as shown in FIG. 8, a second matching layer 2e or a third matching layer 2f is provided to form a multiple matching layer. Was common.
[0008]
That is, the conventional transducer shown in FIG. 7 and FIG. 8 is a subdivided electroacoustic transducer from a transducer composed of one electroacoustic transducer having an acoustic radiation surface shape as shown in FIG. Sixteen are arranged and reconfigured so that the shape and outer diameter of the acoustic radiation surface are equal.
[0009]
Here, since the 16 electroacoustic transducers have the same characteristics, the resonance characteristics of the transducers in which the elements are arranged are the same as those of the transducer of one electroacoustic transducer in FIG. The 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.
[0010]
[Problems to be solved by the invention]
The conventional transducer has the following problems. That is, as shown in FIG. 7, when a transducer having a structure in which a plurality of electroacoustic transducers provided with multiple matching layers is arranged, each electroacoustic transducer is bonded to one piezoelectric vibrator by a method such as adhesion. Since it is formed by attaching two or more matching layers, it is necessary to prevent the gap between the matching layers and to manage the thickness of the adhesive layer. There has been a problem that the variation in characteristics becomes remarkable as the adhesive layer serving as a boundary between the vibrator and the matching layer increases.
[0011]
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.
[0012]
Accordingly, an object of the present invention is to provide an electroacoustic transducer element called a multi-matching layer for the effect of widening the band obtained by providing a single matching layer in an element array type underwater ultrasonic transducer. Broadband transmission / reception that achieves a wider bandwidth by using a combination of electroacoustic transducers with a basic configuration with a single matching layer, without the need for complex structure and increased length. Is to provide a vessel.
[0013]
[Means for Solving the Problems]
The present invention provides an element array type underwater ultrasonic transmitter / receiver configured by arranging a plurality of electroacoustic transducers each having a single matching layer on a piezoelectric vibrator. Two or more types of matching layers having different lengths with respect to the sound wave propagation wavelength λ in each matching layer are used, and the length of each matching layer depends on the use frequency of the transducer and the sound wave propagation speed of the material. The value is set to a value between 1/10 and 4/10 of the sound wave propagation wavelength λ in the matching layer.
[0014]
According to the present invention, a plurality of electro-acoustic transducers with different resonance characteristics can be obtained by providing a plurality of types of matching layers having different dimensions in the length direction, which is the direction of sound wave propagation, to a piezoelectric vibrator of one specification. Thus, by combining them to form an element arrangement, it is possible to obtain a transducer having a sensitivity characteristic obtained by synthesizing the characteristics of the electroacoustic transducer elements having a shifted sensitivity characteristic.
[0015]
That is, the present invention relates to an element array type broadband transducer in which a plurality of electroacoustic transducers each having a single matching layer provided on a piezoelectric vibrator are arranged. However, two or more types of matching layers having different ratios with respect to the sound wave propagation wavelength λ in each matching layer are used, and the length of each matching layer is determined by the use frequency of the transducer and the sound wave propagation speed of the material. This is a broadband transmitter / receiver having a length between 1/10 and 4/10 of the sound wave propagation wavelength λ determined by
[0016]
DETAILED DESCRIPTION OF THE INVENTION
The broadband transmitter / receiver of the present invention will be described below.
[0017]
FIG. 1 is an explanatory diagram of a broadband transducer according to the present invention. Fig.1 (a) shows a front view, FIG.1 (b) shows AA sectional drawing in Fig.1 (a).
[0018]
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.
[0019]
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.
[0020]
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.
[0021]
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. The 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 arranged. However, the resonance point does not increase further.
[0022]
On the other hand, the wideband transducer of the present invention uses a plurality of matching layers having different lengths, thereby obtaining a plurality of electroacoustic transducers with shifted resonance points of the double resonance characteristics and combining them. Thus, a wideband transducer having three or more resonance points is configured.
[0023]
Here, the characteristics of various materials have been evaluated for selecting the material for the matching layer, and the sound propagation medium in the piezoelectric vibrator and the broadband transducer is mainly focused on the acoustic impedance density characteristics of the material. A material having a characteristic value close to the geometric mean value of each acoustic impedance density of water is preferentially selected as the matching layer material. This is because the impedance matching between the piezoelectric vibrator and water which is a sound wave propagation medium is taken into consideration.
[0024]
Regarding the dimension of the matching layer, it is necessary to determine the length dimension in the sound wave propagation direction in particular, but the length dimension L in the sound wave propagation direction as the matching layer with respect to the sound wave propagation wavelength λ at the use frequency of the selected material. It was customary to set L = λ / 4. In the present invention, the length dimension in the sound wave propagation direction of the matching layer is consciously long compared to the conventional method using a uniform matching layer with 1/4 of the sound wave propagation wavelength λ in the matching layer at the operating frequency. A plurality of matching layers having different height dimensions are used.
[0025]
That is, the broadband transducer according to the present invention is an element array type broadband transducer configured by arranging a plurality of electroacoustic transducers each having a single matching layer provided on a piezoelectric vibrator. Two or more matching layers having different lengths in the sound wave propagation direction with respect to the sound wave propagation wavelength λ in each matching layer are used. The length of each matching layer is determined by the frequency and material of the transducer. This is a broadband transmitter / receiver having a length between 1/10 and 4/10 of the sound wave propagation wavelength λ determined by the sound wave propagation speed.
[0026]
Here, when the length of the matching layer is less than 1/10 of the sound wave propagation wavelength λ, the transmittance of the ultrasonic wave in the matching layer is extremely reduced, and the thickness is reduced in terms of dimensions, so that transmission and reception waves are transmitted. The performance of the vessel is significantly reduced. On the other hand, when the length of the matching layer exceeds 4/10 of the sound wave propagation wavelength λ, the transmittance of the ultrasonic wave is extremely lowered, and the performance of the transducer is significantly lowered. Therefore, the length of the matching layer is in the range from 1/10 to 4/10 of the sound wave propagation wavelength λ.
[0027]
【Example】
A broadband transducer according to an embodiment of the present invention will be described below.
[0028]
In the broadband transducer of the present invention, a glass cloth base epoxy resin laminate is used as a material for the matching layer. FIG. 3 is a diagram showing the relationship between the sound wave propagation direction in the glass cloth base epoxy resin laminate and the sound wave propagation direction and the length direction of the matching layer obtained from the resin plate. Here, the glass cloth base material epoxy resin laminated plate 22 has a laminated structure.
[0029]
From FIG. 3, there are two types of matching layers used here, both of which are processed from the glass cloth base epoxy resin laminate 22, and different matching layers are processed from the same material only in the length direction dimension. Are described.
[0030]
Here, the direction along the fiber of the glass cloth base epoxy resin laminate 22 is the sound wave propagation direction of the matching layer, one type is 1/5 the length of the sound wave propagation wavelength λ in the matching layer, and the other type is Two types of matching layers were processed with a length of 3/10 of the wavelength λ. The matching layer is applied by adhesion to the piezoelectric vibrator 21 that resonates in the length direction at a frequency of 70 kHz to obtain two types of electroacoustic transducers 23a and 23b having one matching layer.
[0031]
The material properties of the glass cloth base epoxy resin laminate 22 are: density ρ = 1.9 × 10 ³ (kg / cm ³ ), acoustic wave propagation velocity C = 3150 (m / sec) along the fiber. Therefore, the length dimension in the sound wave propagation direction of the matching layer is about 1/5 of the sound wave propagation wavelength λ with respect to the use frequency of 70 kHz of the prismatic piezoelectric vibrator 21, and is approximately La = 9.0 (mm). At 3/10 of λ, approximately Lb = 13.5 (mm).
[0032]
The piezoelectric vibrator and the two types of matching layers 22a and 22b are bonded with a thermosetting epoxy resin adhesive to obtain electroacoustic transducers 23a and 23b shown in FIG. In addition, FIG. 4 shows the impedance frequency characteristic 24a of the electroacoustic transducer 23a and the impedance frequency characteristic 24b of the electroacoustic transducer 23b. The resonance point of the electroacoustic transducer 23a provided with the matching layer 22a having a large length is about 10 kHz lower than the resonance point of the electroacoustic transducer 23b provided with the matching layer 22b having a small length. shift.
[0033]
By combining these electroacoustic transducers 23a and 23b, a transducer having four resonance points in the impedance characteristic can be obtained. On the other hand, the conventional transducer configuration having one type of matching layer is equivalent to, for example, an arrangement in which only the electroacoustic transducers 23a are arranged, and thus has two resonance points as with the impedance frequency characteristic 24a. It becomes a characteristic.
[0034]
In the embodiment, each of the two types of electroacoustic transducer elements 23a and 23b is used to form a 4 × 4 array, and a cork 25 is bonded between the elements and around the element array to form the elements. Positioning and sound insulation treatment from the surroundings were performed, and after connection with the signal cable 26, the whole was molded with a polyurethane rubber mold 27 to give water tightness, and the element array type underwater ultrasonic transducer shown in FIG. 1 was manufactured.
[0035]
The arrangement of the electroacoustic transducers 23a and 23b in this ultrasonic transducer is arranged alternately as shown in FIG. The sensitivity characteristics of the ultrasonic transducer thus obtained are as shown in the transmission sensitivity frequency characteristic 28 and the reception sensitivity frequency characteristic 30 of the frequency characteristics of the transducer of the present invention shown in FIG.
[0036]
In FIG. 2, as a conventional example, only the matching layer made of the same material as the matching layer used in the embodiment of the transducer shown in FIG. 7 and having a length dimension in the sound wave propagation direction of ¼ of the sound wave propagation wavelength λ is shown. The transmission sensitivity frequency characteristic 29 and the reception sensitivity frequency characteristic 31 when using the are shown together. In contrast to the sensitivity characteristics of the transmitter / receiver obtained with the conventional configuration, in the embodiment of the present invention, the sensitivity characteristics having a wide band on the low frequency side and the high frequency side are obtained.
[0037]
This is because the electroacoustic transducers 23a and 23b used in the embodiment of the present invention have an electroacoustic transducer provided with a matching layer in which the conventional length dimension is ¼ of the sound wave propagation wavelength λ in the matching layer. The sensitivity characteristics of the conversion element are shown shifted to the high frequency side and the low frequency side, respectively. By superimposing the shifted sensitivity characteristics, the band is expanded to the low frequency side and the high frequency side, respectively. By suppressing the sensitivity change in the band, the effect of widening the band as a transducer is obtained.
[0038]
In the conventional handset configuration, compared to the case where a single matching layer is provided, the technique of multiple matching layers for further broadening the band is to provide multiple matching layers to provide multiple resonances for the piezoelectric vibrator. In this method, the increase in sensitivity characteristics in the vicinity of the resonance frequency is continuously connected, and the change in sensitivity within the band is suppressed to achieve a wider band.
[0039]
However, in the handset of the present invention, when a plurality of electrical conversion acoustic elements are divided into several groups to give a shift in resonance characteristics to each element group, and an element array is formed by combining these element groups, One transmitter / receiver can have a plurality of resonance frequencies, and is configured to approximately obtain the same effect as in the case of multiple resonance of a piezoelectric vibrator using multiple matching layers.
[0040]
According to the method of the present invention, it is not necessary to perform complicated characteristic estimation calculation as in the case where a multiple matching layer is added to the piezoelectric vibrator, and a plurality of characteristic estimations are performed when a single matching layer is added. From the combination of characteristics, it is possible to relatively easily estimate the sensitivity characteristics as a transducer after element arrangement.
[0041]
In the above embodiment, a glass cloth base epoxy resin laminate is used as a matching layer, a matching layer having a different length dimension in the sound wave propagation direction of the matching layer is processed, and applied to the piezoelectric vibrator to have different characteristics 2 Although it has been shown that by obtaining only one type of matching layer by obtaining various types of electroacoustic transducers, the effect of broadening the band can be greatly obtained. Only the base epoxy resin laminate is not specified, and the same effect can be obtained even with a general resin material having another uniform composition.
[0042]
However, the magnitude of the effect depends on the characteristics of the material used and the dimension setting of the matching layer. Even when a material different from this example is used, the same effect as this example can be obtained. It is not guaranteed.
[0043]
As described in the present embodiment, the method of obtaining a plurality of types of matching layers from one type of material can omit the work of investigating the characteristics of a plurality of materials and considering the combination of the materials.
[0044]
In addition, even when a plurality of resin materials having different material characteristics are used in combination as the matching layer, the effect of the present invention can be obtained without any problem. However, in this case, even if the length of each matching layer is set to have a different ratio between 1/10 and 4/10 with respect to the sound wave propagation wavelength λ in each resin material, Although the length of the matching layer may be equal depending on the sound wave propagation speed, there is no problem.
[0045]
In this embodiment, the length dimension of the matching layer is intentionally shifted from ¼ of the sound wave propagation wavelength λ in the resin material. However, the length dimension of the matching layer is ¼ of the sound wave propagation wavelength λ. There is no problem in including the setting to be included in the combination.
[0046]
【The invention's effect】
According to the present invention, there is provided a transducer of a system in which electroacoustic transducers having a single matching layer, which is the simplest form with a matching layer, are arranged, and the length of the matching layer with respect to the sound wave propagation wavelength A broadband transmitter / receiver with a wider bandwidth can be provided by a simple method using a plurality of matching layers having different dimension settings.
[Brief description of the drawings]
FIG. 1 is an explanatory diagram of an element array type broadband transducer according to the present invention. 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 a broadband transducer according to the present invention and a broadband transducer according to a conventional configuration. 2A is a diagram showing a relationship between transmission power sensitivity and frequency, and FIG. 2B is a diagram showing a 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 an external view of two types of electroacoustic transducers provided with matching layers having different lengths and an explanatory diagram of characteristics. 4A is an external view of the electroacoustic transducer when the matching layer length is La, and FIG. 4B is an external view of the electroacoustic transducer when the matching layer length is Lb. FIG. 4 and FIG. 4C are diagrams showing impedance characteristics of the respective electroacoustic transducers shown in FIG. 4A and FIG.
FIG. 5 is a cross-sectional view of a conventional transducer using an electroacoustic transducer in which one matching layer is provided in one piezoelectric vibrator, as viewed from the top and side. 5A is a front view of the transducer, and FIG. 5B is a BB cross-sectional view in FIG. 5A.
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. 7A is a front view of the transducer, and FIG. 7B is a CC cross-sectional view in FIG. 7A.
FIG. 8 is a cross-sectional view of a conventional transducer using an electroacoustic transducer in which two matching layers are added to form a multiple matching layer in addition to the transducer shown in FIG.
9 is a conventional transducer using an electroacoustic transducer in which one piezoelectric vibrator is provided with one matching layer, and has a configuration in which the shape of the acoustic radiation surface is the same as that of FIG. Sectional drawing seen from the upper surface and side surface of this. 9A is a front view of the transducer, and FIG. 9B is a DD cross-sectional view in FIG. 9A.
[Explanation of symbols]
1a, 1b, 1c, 21 Piezoelectric vibrators 2a-2g 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 arrangement type broadband transducer in which a plurality of electroacoustic transducers each having a single matching layer provided on a piezoelectric vibrator are arranged, the length of the matching layer in the sound wave propagation direction is set in each matching layer. Two or more types of matching layers having different ratios to the sound wave propagation wavelength λ of the sound wave are used, and the length of each matching layer is determined by the use frequency of the transducer and the sound wave propagation speed of the material. A wideband transducer having a length between 1/10 and 4/10.

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