JPH0638395U - Directional transducer - Google Patents

Abstract

(57) [Summary] [Purpose] In a directional transducer that uses an electroacoustic transducer exclusively for transmitting or receiving, or for both transmitting and receiving, it is possible to measure a wide range of measurement frequencies with a single standard and position. Facilitates alignment. [Structure] A piezoelectric polymer 4 is used as an acoustic transducer, and the piezoelectric polymer 4 is sandwiched between the divided positive electrodes 5a,
5b and 5c and a common negative electrode 6 are provided, and the divided positive electrode 5a
5c is selected according to the measurement frequency.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a directional transducer for underwater acoustics, and more particularly to a directional transducer that can be used in a wide measurement frequency range as a standard device for measuring the sensitivity of a transducer.

[0002]

[Prior art]

 One method of measuring the sensitivity of underwater acoustic wave transmitters and receivers is to measure the wave transmission or reception between the device under test and a standard device whose wave transmission sensitivity or wave reception sensitivity is known. There is a method to convert the sensitivity of the standard device to the transmission or reception sensitivity of the DUT. This measurement method is generally performed in the sea or lakes, but at high frequencies, it can be measured in an aquarium. In these measurements, the reflected waves from the water surface, the tank wall, etc. and the acoustic noise from the surroundings should be negligible compared to the direct waves. Therefore, in order to avoid reflected waves and ambient noise, it is desirable that at least the standard product has an appropriate directivity.

FIG. 2 is a sectional view showing a conventional directional transducer, showing an underwater transducer used as a standard product. In the figure, 1 is a piezoelectric vibrator as an electroacoustic transducer. This piezoelectric vibrator 1 is a disk-shaped piezoelectric vibrator that is generally made of piezoelectric ceramics, for example, PZT (lead titanate / zirconate), is polarized in the thickness direction of the disk, and both sides of the disk are polarized. Positive and negative electrodes are formed at. Reference numeral 2 is a two-core waterproof cable connected to the positive and negative electrodes of the piezoelectric vibrator 1, and 3 is a molded waterproof rubber in order to avoid exposing the conductive parts of the piezoelectric vibrator 1 and the waterproof cable 2.

The directional transducer having this structure uses the thickness vibration mode of the disk of the piezoelectric vibrator 1, and the angle φ _{1 / at} which the sensitivity is reduced to 1/2 with respect to the width of the main pole. _As defined by ₂ , assuming that the wavelength is λ and the diameter of the disk is d, for example, when λ / d = 1.4, a directional transducer with an angle φ _1/2 30 degrees is obtained.

[0005]

[Problems to be solved by the device]

 However, in the directional transducer with the above configuration, when the measurement frequency range is wide, the directivity of the standard product becomes sharp at high frequencies, making it difficult to face the object to be measured. The width becomes wider and becomes more susceptible to noise. Therefore, it was necessary to replace the standards with different directivity depending on the frequency. For example, when d is set to 15 mm, φ is measured when the measurement frequency range is 100 kHz to 300 kHz. _1/2 Is 45 to 14 degrees, which is an appropriate directivity. However, if the measurement frequency range is 50 kHz to 600 kHz, the sensitivity does not drop to 1/2 even at 90 degrees at 50 kHz, and φ at 600 kHz._1/2Was 7 degrees, which made it difficult to measure a wide frequency range.

According to the present invention, when the measurement frequency range is wide, the directivity becomes sharp, and it becomes difficult to position the object to be measured so that it is opposed to the object to be measured. In order to eliminate problems such as susceptibility to ambient noise and ambient noise, at least one of the positive and negative electrodes provided on both sides of the piezoelectric polymer is coaxially divided, and this division is performed. It is an object of the present invention to provide an excellent device capable of measuring a wide range of measurement frequencies with a single standard by selecting the selected electrode.

[0007]

[Means for Solving the Problems]

 The directional transducer according to the present invention uses a piezoelectric polymer as an acoustic transducer, and at least one of the positive electrode and the negative electrode provided on both sides of the piezoelectric polymer is coaxially arranged. It is configured by dividing and the divided electrodes are arbitrarily selected according to the measurement frequency.

[0008]

[Action]

 The present invention does not require replacement of the standard for a wide range of measurement frequencies, and can suppress the influence of noise and facilitate positioning.

[0009]

【Example】

 FIG. 1 is a sectional view showing an embodiment of a directional transducer according to the present invention. In the figure, reference numeral 4 denotes a piezoelectric polymer as an electroacoustic transducer, which is formed in a circular shape having a diameter of 30 mm, for example. As the piezoelectric polymer 4, PVDF (polyvinylidene fluoride), P (VDF-TrFE) (vinylidene fluoride / trifluoroethylene copolymer), P (VDCN-VAC) (vinylidene cyanide / vinyl acetate) are generally used. Copolymers) and the like are known. Reference numerals 5a, 5b and 5c denote split positive electrodes formed by being divided on one surface of the piezoelectric polymer 4, 6 is a common negative electrode formed on the other surface of the piezoelectric polymer 4, and 7 is a common negative electrode. This is a 4-core waterproof cable connected to each of the divided positive electrodes 5a, 5b, 5c and the common negative electrode 6, and outputs three channels. Reference numeral 8 is a waterproof rubber that is molded for waterproofing.

The divided positive electrodes 5a, 5b, 5c and the common negative electrode 6 are formed by Al or Ni vapor deposition or Cu foil adhesion, and the divided positive electrodes 5a, 5b and 5c have the same center. For example, it is divided into circles having diameters of 15 mm and 7.5 mm with a slight width.

Next, when performing measurement using the directional transducer having the above-mentioned configuration, first, if the core wire of the waterproof cable 7 is selected and the channels of the split positive electrode 5 a and the common negative electrode 6 are used, A directional transducer with a 7.5 mm aperture can be constructed. Similarly, if the core wire of the waterproof cable 7 is selected and the two channels of the divided positive electrodes 5a and 5b and the common negative electrode 6 are used in parallel, a directional transducer having a diameter of 15 mm can be constructed. You can Similarly, if the core wire of the waterproof cable 7 is selected and the three channels of the divided positive electrodes 5a, 5b, 5c and the common negative electrode 6 are used in parallel, a directional transducer having a diameter of 30 mm can be constructed. it can. Therefore, if the measurement range is 50 kHz to 150 kHz, 100 kHz to 300 kHz, and 200 kHz to 600 kHz for each opening, the fluctuation of φ _1/2 can be suppressed to 14 degrees to 45 degrees.

In this way, by switching the channel according to the measurement frequency, the range of 50 kHz to 600 kHz can be easily measured without replacing the standard device.

In the above embodiment, the case where three channels are provided adjacent to each other has been described. However, the present invention is not limited to this, and the same can be done even if N (where N ≧ 2) channels are adjacent to each other. Of course. The reason why the N channels can be adjacent to each other is that the acoustic impedance of the piezoelectric polymer is close to the acoustic impedance of water, and the material characteristic that reflection is small is utilized.

In addition to the above-mentioned PVDF, P (VDF-TrFE), P (VDCN-VAC), the piezoelectric polymer as the electroacoustic conversion element may be a rubber material such as PZT (lead titanate / zirgonic acid lead). Of course), and voided PVDF (Void ed Polyvinylidene Fluoride) can also be used. Especially, since the acoustic impedance of this voided PVDF almost matches the acoustic impedance of water, this embodiment is particularly suitable for this embodiment. Are suitable.

Further, the shape of the piezoelectric polymer has been described as a circle, but the shape is not limited to this, and the width of the main pole of directivity in up, down, left and right can be changed in any shape such as a square or an ellipse. Of course, it can be done.

Although the positive electrode is divided and the negative electrode is used as the common electrode in the above description, the present invention is not limited to this, and the negative electrode may be divided and the positive electrode may be used as the common electrode.

The piezoelectric polymer may be divided in correspondence with the division of the positive electrode or the negative electrode, or the groove may be formed in that portion without division.

[0018]

[Effect of device]

 As described above in detail, according to the directional transducer according to the present invention, the piezoelectric polymer is used as the electroacoustic transducer, and the piezoelectric polymer is coaxial with at least one of the positive and negative electrodes. Since the channels are connected according to the measurement frequency, the directivity width can be kept within a certain range. This has the effect of suppressing the effects of noise and eliminating the difficulty of alignment.

[Brief description of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a directional transducer according to the present invention.

FIG. 2 is a cross-sectional view showing a conventional directional transducer.

[Explanation of symbols]

 4 Piezoelectric polymer 5a, 5b, 5c Divided positive electrode 6 Common negative electrode 7 Waterproof cable 8 Waterproof rubber

Claims (3)

[Scope of utility model registration request] 1. A directional transducer which uses an electroacoustic transducer exclusively for transmitting or receiving waves, or for both transmitting and receiving, wherein a piezoelectric polymer is used as the acoustic transducer, and the piezoelectric polymer is removed. A directional transducer that is configured by coaxially dividing at least one of the positive electrode and the negative electrode provided on both sides, and selects the divided electrodes arbitrarily according to the measurement frequency. 2. The directional transducer according to claim 1, wherein the piezoelectric polymer is divided corresponding to the divided electrodes. 3. The directional transducer according to claim 1, wherein a groove is provided in the piezoelectric polymer corresponding to the divided electrodes.