JP2008294719A - Transducer and its driving method - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To obtain a small transducer for oscillating a sound wave of a low frequency in a large bandwidth and with a high output. <P>SOLUTION: A first crooked transducer 10 comprises a diaphragm 11 and a diaphragm of the same shape. A vibrating part 11 comprises a metal disk plate 111 and an active plate 112 embedded in a form of fitted into one surface of the metal disk plate 111. The shape of the active plate 112 is also formed into almost a disk shape. The diaphragm 12 similarly comprises a metal disk plate 121 and an active plate 122. Warpage (dashed line) generated in the first crooked transducer 10 and warpage generated in a second crooked transducer 20 are reverse to each other in phase. Namely, the warp direction of the diaphragm 11 and the warp direction of the diaphragm 21 are reverse to each other, and the warp direction of the diaphragm 12 and the warp direction of the diaphragm 22 are also reverse to each other. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a transmitter that emits a sound wave using a piezoelectric ceramic and a driving method thereof.

  For example, ultrasonic waves or sound waves having a frequency lower than that are used for long-distance sonar and marine resource exploration. For these applications, a sound wave having a low propagation loss in water and a long reach distance of about several kHz is suitable, and in particular, a transmitter capable of transmitting a sound wave of such a frequency is used. . This transmitter is required to be able to oscillate a sound wave of this frequency with a high output, and is also required to be small in size according to the usage situation. However, the energy of the transmitted sound wave becomes smaller when the frequency is low. In general, when the transmitter is downsized, the resonance frequency increases. For this reason, it is difficult to oscillate a low-frequency sound wave with a small transmitter at a high output. In order to achieve a high output at a low frequency, it is particularly necessary to increase the amount of displacement (amplitude) in vibration.

  On the other hand, the frequency emitted by such a transmitter is preferably not variable but variable. For this reason, a wide frequency band of sound waves that can be oscillated is also required.

  As a transmitter satisfying these requirements, for example, there is a transmitter using a piezoelectric ceramic (ceramic) described in Patent Documents 1 and 2. These use the piezoelectric characteristics of the piezoelectric ceramic, that is, the minute displacement generated by minute deformation caused by voltage application. In these cases, a structure has been adopted in which the minute displacement of the piezoelectric ceramic is amplified to increase the amount of displacement finally obtained.

  Patent Document 1 describes a bent disk type transmitter having the structure shown in FIG. The wave transmitter 60 has a structure in which active disk bodies 62 made of piezoelectric ceramics are fitted in recesses formed in a pair of metal disks 61, respectively. These metal disks 61 are bonded together via a metal ring 63 having a low Young's modulus, and are fixed with bolts 64 near the outer periphery of the metal disk 61. In this structure, a protective plate 65 and a urethane resin 66 that protects the periphery of the outer diameter are used. According to this structure, the original displacement amount of the active disk 62, which is a piezoelectric body, is amplified as a deflection of the metal disk 61 in which the active disk member 62 is incorporated, and a large displacement amount can be obtained.

  Patent Document 2 describes a structure in which a metal disk is fixed to the outer peripheral portion of the metal disk through a ring structure having a particularly high strength in a similar structure. In this structure as well, a large amount of displacement could be obtained as well.

  With these structures, it was possible to obtain a transmitter that oscillates high-output sound waves even at low frequencies by amplifying the original displacement amount of the active disk (piezoelectric ceramic) and obtaining a large displacement amount.

  On the other hand, such a piezoelectric vibrator (piezoelectric ceramic) generally has a very high Q value due to its resonance characteristics, and the oscillation frequency bandwidth of the piezoelectric vibrator itself is very narrow. Therefore, in order to obtain a wide frequency band using a piezoelectric ceramic, Patent Document 3 describes a phase of a voltage applied to each vibrator in a structure in which a plurality of cylindrical piezoelectric vibrators are stacked with the central axis aligned. An ultrasonic transducer is described in which the amplitude is controlled to increase the bandwidth. This ultrasonic transducer was particularly suitable as an ultrasonic rangefinder in the air or as a transducer for obstacle search.

JP-A-5-219588 JP-A-5-344582 Japanese Patent Laid-Open No. 10-243498

  Although the transmitters described in Patent Documents 1 and 2 have high output, when they are downsized, the acoustic load is reduced because the radiation surface of the sound wave is also reduced, and the frequency bandwidth is reduced. . Therefore, the frequency band of sound waves that can be oscillated has become narrower. For example, the specific bandwidth (bandwidth / center frequency) is at most about 10 to 20%.

  On the contrary, the bandwidth of the transmitter (ultrasonic transducer) described in Patent Document 3 is sufficiently wide, and the performance is sufficient for ultrasonic oscillation in the atmosphere. However, when the acoustic characteristic impedance is higher than that of the atmosphere, it is impossible to obtain a sufficiently high output, particularly when used in water.

  Therefore, it has been difficult to obtain a small-sized transmitter that oscillates sound waves in a wide frequency band with high output.

  The present invention has been made in view of the above problems, and an object of the present invention is to provide a transmitter and a method for driving the transmitter that solve the above-described problems.

In order to solve the above problems, the present invention has the following configurations.
The gist of the invention described in claim 1 is that there are two diaphragms comprising an active plate made of a piezoelectric ceramic, which is displaced when a voltage is applied, and a metal disk plate in which the active plate is embedded on one surface. However, a plurality of bending-type transmitters that are joined together via a metal ring on the other surface side of the metal disk plate and oscillate sound waves when the two diaphragms vibrate in opposite directions are combined. A plurality of bending wave transmitters having different resonance frequencies are stacked in order of the resonance frequency, and vibrations in adjacent bending wave transmitters are driven as much as possible in opposite phases. It exists in the transmitter characterized by.
The gist of the invention described in claim 2 is that the three or more bent-type transmitters are combined, and the interval between the bent-type transmitters is substantially constant. It exists in a waver.
The gist of the invention described in claim 3 is that the polarization directions of the two active plates in each of the bending wave transmitters are directions perpendicular to the surfaces of the active plates and opposite to each other. It exists in the transmitter of Claim 1 or 2.
The gist of the invention of claim 4 is that, in the plurality of bending-type transmitters, the polarization direction of one active plate in one bending-type transmitter is the other bending-type transmission adjacent to the one active plate. 4. The transmitter according to claim 3, wherein the direction of polarization is the same as the polarization direction of the active plate located on the one active plate side of the wave generator.
The gist of the invention described in claim 5 is that, in the plurality of bending-type transmitters, the polarization direction of one active plate in one bending-type transmitter is different from that of the other bending-type transmission adjacent to the one active plate. 4. The transmitter according to claim 3, wherein the direction of polarization is opposite to the polarization direction of the active plate located on the one active plate side of the wave resonator.
The gist of the invention described in claim 6 is that the frequency characteristics of the oscillation gain of each of the adjacent bent type transmitters are set so as to intersect at a point where the oscillation gain of each of the bent type transmitters is 3 dB to 8 dB lower than the maximum gain. It exists in the transmitter of any one of Claim 1 thru | or 5 characterized by the above-mentioned.
The gist of the invention described in claim 7 is that two diaphragms comprising an active plate made of a piezoelectric ceramic, which is displaced when a voltage is applied, and a metal disk plate in which the active plate is embedded in one surface. However, a plurality of bending-type transmitters that are joined by a metal ring on the other surface side of the metal disk plate and oscillate sound waves when the two diaphragms vibrate in opposite directions are combined. A method of driving a transmitter, wherein the bending frequencies of the bending-type transmitters are made different from each other, and the bending-type transmitters are stacked at a substantially constant interval in order of the resonance frequency. The present invention resides in a driving method of a transmitter, wherein the vibrations in the bending type transmitter to be matched are driven with opposite phases.

  ADVANTAGE OF THE INVENTION According to this invention, the small transmitter which oscillates the sound wave of a wide frequency band with high output can be obtained.

(First embodiment)
FIG. 1 is a diagram showing a configuration of a transmitter according to the first embodiment of the present invention. The transmitter 1 includes a first bent type transmitter 10 and a second first bent type transmitter 20. These bending type transmitters are driven by the same AC oscillator, and oscillate sound waves according to their frequencies. Both the first bent type transmitter 10 and the second first bent type transmitter 20 have a substantially disc shape, and FIG. 1 shows a sectional view of the laminated structure. In addition, the sound wave here includes an ultrasonic wave in addition to a sound wave that is audible to humans.

  The first bending-type transmitter 10 includes a diaphragm 11 and a diaphragm 12 having the same shape. The vibration part 11 includes a metal disk plate 111 and an active plate 112 embedded in a form fitted to one surface thereof. The shape of the active plate 112 is also a substantially disk shape. Similarly, the vibration plate 12 includes a metal disk plate 121 and an active plate 122.

  The metal disk plates 111 and 121 are made of an aluminum alloy. The active plates 112 and 122 are made of a piezoelectric material, for example, hard lead zircon titanate-based piezoelectric ceramics, and are fixed to the metal disk plates 111 and 121 with an adhesive or the like. In addition, spontaneous polarization is imparted so that the active plates 112 and 122 have piezoelectric characteristics. This direction is the direction indicated by the white arrow in FIG. 1, and is the upper side of the active plate 112 and the lower side of the active plate 122, that is, the reverse direction. Electrodes (not shown) are respectively formed on the upper side of the active plate 112 and the lower surface of the active plate 122 in FIG. 1, and these electrodes are electrically connected and connected to the input 1. . Metal disk plates 111 and 121 are also electrically connected and connected to input 2.

  A convex ring 13 having a ring shape is provided on the outer peripheral portion of the other surface of the diaphragm 11 as viewed from the surface on which the active plate 112 is formed. A concave ring 14 is provided on the outer peripheral portion of the other surface of the diaphragm 12 as viewed from the surface on which the active plate 122 is formed. As shown in FIG. 1, the diaphragms 11 and 12 are fixed in a shape in which the convex ring (metal ring) 13 and the concave ring (metal ring) 14 are fitted on the outer periphery. Therefore, in the first bending type transmitter 10, the active plate 112 is exposed on the upper side and the active plate 122 is exposed on the lower side. For this fixing, an adhesive or a bolt (not shown) is used. The convex ring 13 and the concave ring 14 are ring-shaped and made of a metal material having high wear resistance such as Cr-Mo steel. In addition, the space | interval of the diaphragm 11 and the diaphragm 12 after an assembly can be adjusted by adjusting the shape of the convex ring 13 and the concave ring 14.

About the above 1st bending | flexion type | mold wave transmitter 10, it is the same as that of the thing of patent document 1,2. That is, when an AC signal is applied between the input 1 and the input 2, a displacement (vibration) corresponding to the active plate 112 is generated due to the piezoelectric effect. When the radial displacement of the disk generated in the active plate 112 occurs, the metal disk plate 111 is deformed accordingly. However, since it is fixed at the outer periphery, the vibration plate 11 has a dotted line in FIG. Deflection as shown in FIG. That is, the diaphragm 11 is caused to bend and vibrate around the periphery. In this case, the electromechanical coupling coefficient of the diameter spreading vibration is about 50 to 55%. Similarly, the diaphragm 12 also bends, but due to the polarization direction and the electrode configuration, the bend is in the opposite direction to the diaphragm 11 as indicated by the broken line in FIG. This bending occurs according to the frequency applied to the active plate, and a sound wave corresponding to this is oscillated. The oscillation gain of the sound wave is maximized at a resonance frequency (first resonance frequency f ₁ ) determined by the configuration (material, geometric configuration) of the diaphragm 11 and the diaphragm 12. Since the amplitude of this vibration is larger than the amplitude of the vibration in the radial direction of the active plate, a sound wave is oscillated at a high output. Further, as described in Patent Documents 1 and 2, the bending wave transmitter 10 can oscillate a high-output sound wave at a low frequency even if it is small.

The configuration of the second bent type transmitter 20 is the same as that of the first bent type transmitter 10. That is, the diaphragms 21 and 22 are joined via the convex ring (metal ring) 23 and the concave ring (metal ring) 24. The vibration plate 21 includes a metal disk plate 211 and an active plate 212, and the vibration plate 22 includes a metal disk plate 221 and an active plate 222. However, the outer diameters of the diaphragms 21 and 22 are smaller than those of the diaphragms 11 and 12. For this reason, the frequency (second resonance frequency f ₂ ) at which the oscillation gain of the sound wave oscillated by the second bending-type transmitter 20 is maximized is higher than the first resonance frequency. Moreover, the space | interval of the 1st bending wave transmitter 10 and the 2nd bending wave transmitter 20 can be set suitably.

  Here, as shown in FIG. 1, in FIG. 1, the polarization direction of the active plate 212 is the lower side, and the polarization direction of the active plate 222 is the upper side. Alternatively, the polarization direction of the lower active plate 122 in the bending wave transmitter 10 is the same as the polarization direction of the active plate 212 located on the active plate 122 side in the bending wave transmitter 20. That is, in the first bent type transmitter 10 and the second bent type transmitter 20, their polarization directions are opposite to each other.

  On the other hand, the upper electrode of the active plate 212 and the lower electrode of the active plate 222 are electrically connected and connected to the input 1. Similarly, the metal disk plate 211 and the metal disk plate 221 are electrically connected and connected to the input 2. Therefore, when an AC signal is applied between the input 1 and the input 2, the vibrators in the first bent wave transmitter 10 and the second bent wave transmitter 20 vibrate in the opposite directions in accordance with this. Sound waves corresponding to the AC frequency are oscillated.

  At this time, as shown in FIG. 1, the bending (broken line) generated in the first bent type transmitter 10 and the second bent type transmitter 20 has an opposite phase. That is, the direction in which the diaphragm 11 is bent and the direction in which the diaphragm 21 is bent are opposite, and the direction in which the diaphragm 12 is bent and the direction in which the diaphragm 22 is bent are also opposite.

When this state is expressed by an equivalent circuit, it means that a transformer having a transformation ratio of −1: 1 is built in the bending type transmitter 20. Since this transformer works effectively, the transmitter shown in FIG. 1 forms a multimode filter with water as a load, which is more than three times the single mode ratio bandwidth of the individual bending transmitters 10 and 20. A specific bandwidth can be obtained. FIG. 2 shows an equivalent circuit as viewed from the electrical system when these bending wave transmitters 10 and 20 are driven in this state. In FIG. 2, Cd ₁ , L ₁ , R ₁ , C ₁ , and Z _L1 represent the braking capacity, equivalent mass, equivalent mechanical resistance, equivalent compliance, and load resistance of the bending type transmitter 10, respectively. Cd ₂ , L ₂ , R ₂ , C ₂ , and Z _L2 represent the braking capacity, equivalent mass, equivalent mechanical resistance, equivalent compliance, and load resistance of the bending-type transmitter 20, respectively. The −1: 1 transformer appears when the bending type transmitter 10 is opposite to the bending type transmitter 20 because the polarization directions of the piezoelectric ceramic active disk are opposite to each other. With this transformer, the transmitter 1 functions as a differential connection type multimode filter in an equivalent circuit.

Therefore, the frequency dependence of the oscillation gain of the transmitter 1 is as shown by the solid line in FIG. Here, the characteristics of the broken line are characteristics when the electrical connection is changed and the bending transmitter 10 vibrates the bending transmitter 20 in the same phase. f ₁ is the resonance frequency of the bending transmitter 10, and f ₂ is the resonance frequency of the bending transmitter 20. Regardless of the reverse phase and the same phase, the transmission gain has a maximum value when the frequencies are f ₁ and f ₂ , but in the case of the reverse phase (solid line) due to the effect of the transformer in the equivalent circuit, f ₁ and never its output is greatly reduced even between f _2. On the other hand, in the case of in-phase (broken line), because there is no effect of the transformer, there is a region of greatly reduced between f ₁ and f _2. Therefore, by setting the opposite phase, it is possible to oscillate sound waves in a wider frequency band.

Here, even when the bending type transmitter 10 and the bending type transmitter 20 are driven in opposite phases, the output between f ₁ and f ₂ is smaller than these maximum values. . In order to reduce this decrease value and make the characteristic between f ₁ and f ₂ nearly flat, the oscillation gain characteristic of the bending-type transmitter 10 alone and the bending transmitter 20 alone The point where the oscillation gain characteristic intersects is preferably in a region 3 dB to 8 dB lower than the respective maximum gains (values at f ₁ and f ₂ ).

As described above, each of the bending type transmitters 10 and 20 is small and can oscillate a sound wave with high output. Although the resonance frequencies (f ₁ , f ₂ ) are different from each other, by combining them into the transmitter 1 having the configuration shown in FIG. 1, the oscillation frequency band, that is, a value greater than a certain oscillation gain is obtained. The frequency band can be widened. Therefore, this transmitter becomes a small-sized transmitter that oscillates sound waves in a wide frequency band with high output.

  In this transmitter, the bending transmitters 10 and 20 are driven in opposite phases, but in order to perform this operation, a configuration different from that shown in FIG. FIG. 4 is a diagram showing the configuration of the transmitter 2. In this transmitter 2, the polarization directions in the active plates are different and the electrical connections are different. That is, the polarization directions of the active plates 212 and 222 are opposite to those of the transmitter 1, and the polarization direction of the lower active plate 122 in the bending transmitter 10 is the bending transmitter 20. The direction of polarization of the active plate 212 located on the active plate 122 side is opposite to the direction of polarization. 1 is the same as the transmitter 1 in FIG. 1 in that the polarization directions of the active plates in the same bending type transmitter are opposite to each other. Further, the upper electrode of the active plate 212 and the lower electrode of the active plate 222 are electrically connected, and are connected to the input 1 together with the metal disk plate 111 and the metal disk plate 121. The metal disk plate 211 and the metal disk plate 221 are electrically connected, and are connected to the input 2 together with the lower electrode of the active plate 112 and the upper electrode of the active plate 122.

  Also in the transmitter 2, when an AC signal is applied between the input 1 and the input 2, the bending transmitters 10 and 20 are driven in opposite phases. Therefore, an effect similar to that of the transmitter 1 is brought about.

  In both of the above examples, the polarization directions of the two active plates in each bending wave transmitter are opposite to each other, but the present invention is not limited to this. Even when these polarization directions are set to the same direction, the same effect can be obtained as long as the configuration can perform the same operation as in the above example. In addition, the same effect can be obtained as long as the same operation can be realized.

  In addition, as described in Patent Documents 1 and 2, by making each metal disk plate and each active plate substantially disk-shaped, it can be particularly high output, but is not limited thereto, These shapes can also be set as appropriate.

(Second Embodiment)
In the first embodiment, the example using the two bent transmitters 10 and 20 having different resonance frequencies is described, but the number thereof may be three. FIG. 5 is a diagram showing the configuration of the transmitter 51.

In this transmitter 51, in addition to the first bent type transmitter 10 and the second bent type transmitter 20, a third bent type transmitter 30 is also used. Are arranged at substantially equal intervals. The first and second bending wave transmitters 10 and 20 are the same as those in the case of the transmitter 1. Similarly to these, the third bending-type transmitter 30 has diaphragms 31 and 32 joined together via a convex ring (metal ring) 33 and a concave ring (metal ring) 34. The vibration plate 31 includes a metal disk plate 311 and an active plate 312, and the vibration plate 32 includes a metal disk plate 321 and an active plate 322. However, the outer diameters of the diaphragms 31 and 32 are smaller than those of the diaphragms 21 and 22. For this reason, the frequency (third resonance frequency f ₃ ) at which the oscillation gain of the sound wave oscillated by the third bending-type transmitter 30 is maximized is higher than the second resonance frequency f ₂ . Therefore, these three bending-type transmitters are stacked in order of their resonance frequencies. Moreover, these intervals are substantially constant.

  Further, the polarization directions of the active plates 112, 222, and 312 are the same, and are downward in FIG. Similarly, the polarization directions of the active plates 122, 212, and 322 are the same, and are downward in FIG. That is, the polarization directions of the two active plates in the same bending type transmitter are directions perpendicular to the surfaces, and the two plates are opposite to each other. Also, the polarization direction of one active plate in one bending type transmitter is the polarization direction of the active plate located on the side of this active plate in another bending type transmitter adjacent to this one active plate. It is the same direction. In other words, the polarization direction of each active plate is opposite in the adjacent bending type transmitter.

  The upper electrodes of the active plates 112, 212, and 312 and the lower electrodes of the active plates 122, 222, and 322 are electrically connected to each other and are connected to the input 1. The metal disk plates 111, 121, 211, 221, 311, 321 are electrically connected to each other and are connected to the input 2.

  FIG. 6 is a schematic diagram showing the configuration of the transmitter 51. As shown in FIG. 5, the bending wave transmitters 10, 20, and 30 are stacked at equal intervals in order from the top. Each bending type transmitter is fixed to a wire 91 serving as a support by a transmitter support 90. In FIG. 6, each wiring shown in FIG. 5 is omitted, but the wiring can be appropriately performed using soldering or the like.

The bending of each diaphragm in this configuration is indicated by a broken line in FIG. In other words, the bending-type transmitters 10, 20, and 30 operate in a state in which the phase of vibration is different by 180 degrees from the top. Further, the resonance frequencies f ₁ , f ₂ , and f ₃ become higher from the top to the bottom.

An equivalent circuit of the transmitter 51 is shown in FIG. In FIG. 7, Cd ₃ , L ₃ , R ₃ , C ₃ , and Z _L3 represent the braking capacity, equivalent mass, equivalent mechanical resistance, equivalent compliance, and load resistance of the bending type transmitter 30, respectively. Cd ₁ etc., Cd ₂ etc. are the same as those in the first embodiment. Also in this case, a -1: 1 transformer appears in the equivalent circuit, and the transmitter 51 functions as a differential connection type multimode filter in the same manner as the transmitter 1 by this transformer. The frequency dependence of the oscillation gain is as shown in FIG. In other words, although the resonance frequencies f ₁ , f ₂ , and f ₃ of the bending wave transmitters 10, 20, and 30 have peaks, it is possible to oscillate frequencies with a wide bandwidth as a whole. In particular, by combining bent-type transmitters having three different resonance frequencies, a high oscillation gain can be obtained in a wider frequency band than in the case of the first embodiment.

In order to broaden this bandwidth particularly effectively, the portion where the oscillation gain characteristics of each bending wave transmitter itself intersect is 3 dB to 8 dB lower than the maximum value, as in the first embodiment. It is preferable to set f ₁ , f ₂ , and f ₃ as much as possible. For this purpose, the geometric dimensions of each bending type transmitter are set as appropriate, and the resonance frequency is set.

  Also, each bending type transmitter is the same as that described in Patent Documents 1 and 2, as in the first embodiment. That is, it is small and can oscillate sound waves with high output. Therefore, the transmitter 51 is a small transmitter that oscillates a sound wave in a wide frequency band with a high output.

  When each diaphragm operates in the same manner as described above, it is obvious that the same effect can be obtained even when the polarization method and the electrical connection method of each active plate are different. Moreover, as described in Patent Documents 1 and 2, it is preferable that each metal disk plate and each active plate have a substantially disk shape in order to obtain a high output, but the invention is not limited thereto. The shape can be set as appropriate. Similarly, in order to obtain a high output, it is preferable that the interval between the bending-type transmitters is substantially constant, but can be set as appropriate.

  Details of the embodiments of the present invention will be described below.

Example 1
As Example 1, a transmitter having the structure shown in FIG. 1 was manufactured by combining two bent transmitters. Here, each active plate in the first bending type transmitter is a hard lead zirconate titanate-based piezoelectric ceramic, and is a disc having a thickness of 10 mm and a diameter of 150 mm. Each metal disk plate was made of an aluminum alloy, a circular plate having a maximum thickness of 20 mm and a diameter of 200 mm, and the active plate was embedded in the surface using an adhesive. Both the convex ring and the concave ring (metal ring) were made of Cr-Mo steel, the outer diameter was 200 mm, and the inner diameter was 190 mm. The interval between the convex portions and the concave portions was set so that the interval between the metal disk plates after assembly was 2 mm. Fixing at the time of assembly was performed by bolts. The resonance frequency f ₁ in the first bent type transmitter was 3.5 kHz.

Each material in the second bent type transmitter was the same as that of the first bent type transmitter, and both active plates were discs having a thickness of 9 mm and a diameter of 120 mm. The metal disk plate had a thickness of 18 mm and a diameter of 150 mm. Both the convex ring and the concave ring were made of Cr-Mo steel, the outer diameter was 150 mm, and the inner diameter was 142 mm. The interval between the convex portions and the concave portions was set so that the interval between the metal disk plates after assembly was 2 mm. The resonance frequency f2 of the _second bent type transmitter was 4.6 kHz.

  A transmitter having the configuration shown in FIG. 1 was created by combining the above bent transmitters with an interval of 180 mm. In this case, the portion where the oscillation gain characteristics of the respective bending type transmitters intersect each other has a characteristic of intersecting when it is 7 dB below the maximum value. As a result, as shown in FIG. 3, a characteristic with a -6 dB ratio bandwidth of 48% was obtained. On the other hand, the -6 dB relative bandwidth of each bent-type transmitter was at most 15%. Therefore, a broadband characteristic more than twice that was obtained.

(Example 2)
As Example 2, a transmitter having the structure shown in FIG. 4 was manufactured by combining three bent transmitters. Here, the first and second bending wave transmitters are the same as those in the first embodiment. The same material was used for the third bent type transmitter, and both active plates had a thickness of 8 mm and a diameter of 90 mm. Each metal disk plate was made of an aluminum alloy, its maximum thickness was 16 mm, and a disk with a diameter of 120 mm, and the active plate was embedded in its surface using an adhesive. Both the convex ring and the concave ring were made of Cr-Mo steel, the outer diameter was 120 mm, and the inner diameter was 114 mm. The interval between the convex portions and the concave portions was set so that the interval between the metal disk plates after assembly was 2 mm. The resonance frequency _{f 3} of the third bending-type wave transmitter was 6.1KHz.

  The above-described bending type transmitters were combined at an interval of 150 mm to produce a transmitter having the configuration shown in FIGS. With this configuration, the characteristics intersected when the maximum gains of the first to third bending type transmitters were lowered by 3 dB to 8 dB. As a result, as shown in FIG. 7, a characteristic with a -6 dB relative bandwidth of 54% was obtained. On the other hand, the -6 dB relative bandwidth of each bent-type transmitter was at most 15%. Therefore, a broadband characteristic more than three times that was obtained.

It is sectional drawing which shows the structure of an example of the transmitter used as the 1st Embodiment of this invention. It is a figure which shows the equivalent circuit of operation | movement of the transmitter used as the 1st Embodiment of this invention. It is a figure which shows the frequency characteristic of the oscillation gain of the transmitter used as the 1st Embodiment of this invention. It is sectional drawing which shows the structure of the other example of the transmitter used as the 1st Embodiment of this invention. It is sectional drawing which shows the structure of an example of the transmitter used as the 2nd Embodiment of this invention. It is an external view which shows the structure of an example of the transmitter used as the 2nd Embodiment of this invention. It is a figure which shows the equivalent circuit of operation | movement of the transmitter used as the 2nd Embodiment of this invention. It is a figure which shows the frequency characteristic of the oscillation gain of the transmitter used as the 2nd Embodiment of this invention. It is a figure which shows an example of a structure of the conventional transmitter.

Explanation of symbols

1, 2, 51, 60 Transmitter 10, 20, 30 Bent transmitter 11, 12, 21, 22, 31, 32 Vibration plate 111, 121, 211, 221, 311, 321 Metal disk plate 112, 122 , 212, 222, 312, 322 Active plate 13, 23, 33 Convex ring (metal ring)
14, 24, 34 Concave ring (metal ring)
61 Metal disc 62 Active disk 63 Metal ring 64 Bolt 65 Protection plate 66 Urethane resin 90 Transmitter support 91 Wire

Claims (7)

The other surface of the metal disk plate is an active plate made of a piezoelectric ceramic that is displaced when a voltage is applied, and two vibration plates comprising a metal disk plate in which the active plate is embedded on one surface. A transmitter which is combined with a plurality of bending-type transmitters which are joined together via a metal ring on the side and oscillate sound waves when the two diaphragms vibrate in opposite directions,
A plurality of bending-type transmitters having different resonance frequencies are stacked in order of the resonance frequency, and vibrations in adjacent bending-type transmission devices are driven to have opposite phases. vessel.   The transmitter according to claim 1, wherein three or more bent-type transmitters are combined, and the interval between the bent-type transmitters is substantially constant.   3. The transmission according to claim 1, wherein the polarization directions of the two active plates in each of the bending wave transmitters are directions perpendicular to the surface of the active plate and opposite to each other. Waver.   In the plurality of bending-type transmitters, the polarization direction of one active plate in one bending-type transmitter is the side of the one active plate in another bending-type transmitter adjacent to the one active plate. The transmitter according to claim 3, wherein the transmitter is in the same direction as the polarization direction of the active plate located at the center.   In the plurality of bending-type transmitters, the polarization direction of one active plate in one bending-type transmitter is the side of the one active plate in another bending-type transmitter adjacent to the one active plate. The transmitter according to claim 3, wherein the transmitter is in a direction opposite to the polarization direction of the active plate located at the position.   2. The frequency characteristic of the oscillation gain of each of the adjacent bent type transmitters is set so that the oscillation gain of each of the bent type transmitters intersects at a point 3 dB to 8 dB lower than the maximum gain. The transmitter of any one of thru | or 5. The other surface of the metal disk plate is an active plate made of a piezoelectric ceramic that is displaced when a voltage is applied, and two vibration plates comprising a metal disk plate in which the active plate is embedded on one surface. A method of driving a transmitter in which a plurality of bending-type transmitters that are joined together via a metal ring on the side and oscillate sound waves by vibrating the two diaphragms in opposite directions,
The resonance frequency of each of the bending wave transmitters is made different, and a plurality of the bending wave transmitters are stacked at a substantially constant interval in order of the resonance frequency,
A method of driving a transmitter, wherein vibrations in adjacent bending-type transmitters are driven in opposite phases.

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