JP3406986B2 - Ultrasonic transducer and its vibration control method - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electroacoustic conversion technology, and in particular, it is a small-sized and light-weight wideband piezoelectric ultrasonic transducer for use in sonars and the like, and a vibration thereof. Regarding control method.

[0002]

2. Description of the Related Art Conventionally, several kHz to several tens of kHz in water.
As a wideband ultrasonic transducer that is capable of high-power transmission in the z frequency band and is highly efficient, an ultrasonic transducer in which an acoustic matching layer is provided on the front mass of a bolted Langevin type transducer is known. (IEEE Proceedings, Vol.131,
Part F, No.3, pp.285-297, June 1984 etc.).

Further, as a band broadening technique for a bolted Langevin type transducer, as shown in FIG. 4, a recess 10 is provided in the front mass 3 of the Langevin type oscillator.
There is an ultrasonic wave transmitter / receiver (hereinafter referred to as a wave transmitter / receiver) in which the flexural vibration plate 5 is provided in the recess 10. In the figure, 1 is a piezoelectric ceramic laminate, 2 is a rear mass, 4 is a rear mass 2
2 shows a bolt connecting the front mass 3 and the front mass 3.

This wave transmitter / receiver has a wide band by superimposing two modes of the longitudinal vibration mode of the Langevin type wave transmitter / receiver and the bending vibration mode of the bending diaphragm 5. This method has advantages such as smaller size and lighter weight than a method using a matching layer.

[0005]

The first problem of the prior art described above is that the lower limit frequency of the bandwidth is the longitudinal vibration resonance frequency of the transducer, so it is determined by the overall length of the transducer. In other words, in order to reduce the frequency, the size of the transmitter / receiver becomes large.

The reason for this is that the lowest resonance frequency is the longitudinal vibration resonance frequency of the entire transducer, regardless of the method of providing the acoustic matching layer and the method of providing the bending vibration plate of the prior art. Therefore, the lower limit frequency of the widened bandwidth is the longitudinal vibration resonance frequency of the entire transducer, and it cannot be widened to a frequency lower than this frequency. Therefore, in order to further reduce the operating frequency, it is necessary to lower the longitudinal vibration resonance frequency determined by the overall length dimension of the wave transmitter / receiver, which increases the overall length dimension.

The second problem is that it is structurally difficult to make the band wider.

The reason is that, in the method of providing the acoustic matching layer, if a plurality of acoustic matching layers are provided in order to widen the bandwidth, the adhesive portion of the acoustic matching layer increases and the reliability deteriorates. Since it has a large size,
The practical number of matching layers is limited to 2 or 3. Even when using multiple matching layers, the specific bandwidth is limited to about 60%, and it is difficult to further increase the bandwidth.

Further, in the method of providing the bending vibration plate, there are two modes of the longitudinal vibration mode of the transducer and the bending vibration mode of the bending vibration plate.
Since the two modes are superposed and the band is widened, it is necessary to properly set the respective resonance frequencies so that the two modes are well coupled. In this case, the specific bandwidth is limited to about 80%, and it is difficult to further increase the bandwidth due to the structure.

Therefore, an object of the present invention is to provide a wideband piezoelectric ultrasonic transducer and a method of vibrating a flexural vibrating body, which can solve the above-mentioned problems and can realize a small size, a light weight, a low frequency, and a wider band. To do.

[0011]

In order to solve the above problems, in the present invention, a piezoelectric ceramic laminate having internal through holes is arranged between a front mass and a rear mass, and the piezoelectric ceramic laminate is provided on the piezoelectric ceramic laminate. In an ultrasonic transducer including a bolted Langevin type transducer provided with a bolt for applying a compressive stress to a piezoelectric ceramic laminate through a through hole, a concave portion is provided on the front face of the front mass, and the piezoelectric thin plate ceramic and the inside are provided in the concave portion. The flexural vibrating body, to which the vibrating plate having the cavity is attached, is provided so as to float above the bottom of the recess of the front mass so that the piezoelectric thin plate ceramic is inside the recess.

In this case, the inner diameter of the concave portion of the front mass is set to 80% or more of the total diameter of the front mass, and the diameter of the cavity of the diaphragm is set to about 50% to 70% of the total diameter of the front mass. It is very suitable.

In addition, the piezoelectric thin plate ceramic is driven so that the bending vibration modes of the entire bending vibration member provided in the recess of the front mass are in opposite phases to the longitudinal vibration fundamental resonance mode of the bolted Langevin type vibrator. It is also possible to shift the voltage phase and set the structural dimensions so that the bending vibration resonance frequency of the entire bending vibration body is lower than the longitudinal vibration resonance frequency of the bolted Langevin type vibrator.

Further, the longitudinal vibration fundamental resonance mode of the bolted Langevin type vibrator is opposite in phase to the bending vibration mode of the plate outside the cavity of the diaphragm constituting the bending vibrator provided in the concave portion of the front mass. And the structural dimensions can be set so that the flexural vibration resonance frequency of the plate outside the cavity of the diaphragm is higher than the longitudinal vibration resonance frequency of the bolted Langevin type vibrator. it can.

On the other hand, according to the method of the present invention, the bending vibration provided in the concave portion of the front mass of the ultrasonic transducer including the Langevin type vibrator for bolting the front mass and the rear mass with the piezoelectric ceramic laminate interposed therebetween. A vibration control method for vibrating a body, comprising a flexural vibrating body in which a vibrating plate having a cavity inside and a piezoelectric thin plate ceramic are bonded together, and the piezoelectric thin plate ceramic is placed inside the concave part from the bottom of the concave part. It is placed in a floating state, and the phase of the driving voltage of the piezoelectric thin plate ceramic is shifted so that the bending vibration mode of the entire bending vibration body has a phase opposite to the longitudinal vibration basic resonance mode of the Langevin type vibrator. Was applied.

In this case, the inner diameter of the concave portion of the front mass is set to 80% or more of the total diameter of the front mass, and the diameter of the cavity of the diaphragm is set to about 50% to 70% of the total diameter of the front mass. It is very suitable.

Further, the longitudinal vibration fundamental resonance mode of the Langevin type oscillator is set so that the bending vibration modes of the plates outside the cavity of the vibration plate constituting the bending vibration body have mutually opposite phases, and The structural dimensions can be set such that the flexural vibration resonance frequency of the plate outside the cavity of the diaphragm is higher than the longitudinal vibration resonance frequency of the Langevin type vibrator.

The transducer according to the present invention has three vibration modes, and a bending vibration mode of a bending vibration body in which a piezoelectric thin plate ceramic and a vibration plate having a cavity inside are bonded in order of increasing frequency, Langevin. There are a longitudinal vibration mode of the die transducer and a bending vibration mode of a plate outside the cavity of the diaphragm having a cavity inside.

The longitudinal vibration fundamental resonance mode of the Langevin type oscillator is such that the bending vibration mode of the entire bending vibration body and the bending vibration mode of the plate outside the cavity of the vibration plate constituting the bending vibration body are in opposite phases to each other. Since the three vibration modes are coupled to each other, the bandwidth can be significantly widened.

Further, since the flexural vibration resonance frequency of the flexural vibration body in which the piezoelectric thin plate ceramic and the vibration plate having a cavity inside are bonded together is lower than the longitudinal vibration resonance frequency of the Langevin type transducer, The bandwidth can be extended to the low frequency region without increasing the size of the container.

[0021]

BEST MODE FOR CARRYING OUT THE INVENTION Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. Referring to FIG. 1, 11 is a hollow piezoelectric ceramic laminate, 12 and 1
3 is rear mass, front mass, 14 is bolt,
Reference numeral 15 is a bending vibration body.

The bending vibration body 15 is a piezoelectric thin plate ceramic 1.
6 and a diaphragm 17 having a cavity 177 inside are bonded together with a strong adhesive.
The surface where the piezoelectric thin plate ceramic 16 is not bonded is a plate 18 that causes bending vibration when viewed from the cavity 177 part of
This surface is the acoustic emission surface.

There is a hole in the center of the rear mass 12,
A tap is cut at the center of the front mass 13. Static stress bias is applied to the piezoelectric ceramic laminate 11 by the rear mass 12, the front mass 13, and the bolts 14. The flexural vibration body 15 is fitted into the concave portion 10 provided on the upper surface of the front mass 13 so that the piezoelectric thin plate ceramic 16 is located inside, and the flexural vibration body 15 and the front mass 1 are fitted.
The joint portion 3 is welded and completely integrated. Further, a phase shifter 19 is attached so that the phase can be shifted when a drive voltage is applied to the piezoelectric thin plate ceramic 16.

Next, the operation will be described. The transducer of the present invention has three vibration modes, and a bending vibration body 1 in which a piezoelectric thin plate ceramic 11 and a vibration plate 17 having a cavity 177 inside are bonded in order of increasing natural resonance frequency.
5, the frequency f1 of the peripheral fixed bending vibration mode, the frequency f2 of the longitudinal vibration mode of translational vibration in the entire Langevin type transducer, and the peripheral fixed bending of the plate 18 outside the cavity 177 of the diaphragm 17 having the cavity 177 inside. It is the frequency f3 of the vibration mode.

FIG. 2 shows a vibration mode diagram for each vibration mode. These three vibration modes are
The inner diameter of the recess 10 of the front mass 13 is set to 80% or more of the total diameter of the front mass 3, and the cavity 17 of the diaphragm 17 is set.
By setting the diameter of the seven parts to about 50 to 70% of the total diameter of the front mass, the relationship of f1 <f2 <f3 can be obtained.

Further, the piezoelectric thin plate ceramic 16 is arranged so that the bending vibration modes of the entire bending vibration member 15 provided on the upper surface of the front mass 13 are opposite to the longitudinal vibration resonance mode of the entire Langevin type transducer. The phase of the drive voltage is shifted.

Further, with respect to the longitudinal vibration resonance mode of the Langevin type transducer, the bending vibration modes of the plate 18 outside the cavity 177 of the vibration plate 17 constituting the bending vibration body 15 provided on the upper surface of the front mass 13 are mutually different. It will be in reverse phase.

That is, in the translational displacement longitudinal vibration mode, when the Langevin type transducer is extended, the acoustic radiation surface vibrates so as to extend in the direction of removing the medium as shown in FIG.
In the bending vibration mode of the entire bending vibration body 15 provided on the upper surface of the front mass 13 and the bending vibration mode of the plate 18 outside the cavity 177 of the vibration plate 17 constituting the bending vibration body 15 provided on the upper surface of the front mass 13, As shown in, when the Langevin type transducer is contracted, it bends and vibrates in the direction of medium exclusion. By the driving in which the phases are opposite to each other, the respective modes are superposed and the band is widened.

As is apparent from the above description, in the transducer of the present invention, the longitudinal vibration mode of the Langevin type transducer, the bending vibration mode of the entire bending vibration body 15, and the bending vibration body 15 are constituted. Since three vibration modes of the bending vibration mode of the plate 18 outside the cavity 177 of the vibration plate 17 can be superimposed, the bandwidth can be significantly widened as compared with the conventional product.

Further, the flexural vibration resonance frequency of the flexural vibration body 15 in which the piezoelectric thin plate ceramic 16 and the vibration plate 17 having the cavity 177 are bonded together is lower than the longitudinal vibration resonance frequency of the Langevin type transducer. Therefore, the bandwidth can be expanded to the low frequency region without increasing the size of the transducer.

Next, the first embodiment of the present invention will be described more specifically with reference to the drawings. In FIG. 1, a piezoelectric ceramic laminate 11 is a ring made of lead zircon titanate-based piezoelectric ceramics polarized in the thickness direction. Adjacent rings are arranged so that their polarization directions are opposite to each other. They are electrically connected in parallel.

The piezoelectric thin plate ceramic 16 is a disk made of lead zircon titanate-based piezoelectric ceramics polarized in the thickness direction, and a piezoelectric ceramic laminated body through a phase shifter 19 for shifting the phase of the driving voltage by 180 degrees. 11 is connected in parallel.

Metal masses 12 and 13 respectively form a rear mass and a front mass. The bolt 14 is made of steel and applies a static compression bias to the piezoelectric ceramic laminate 11.

Reference numeral 17 is a diaphragm made of an aluminum alloy and having a disk-shaped cavity 177 therein.
Is firmly fixed with an epoxy-based strong adhesive to form the bending vibration body 15.

The joint portion between the front mass 13 and the bending vibration body 15 was integrated by welding. The inner diameter of the recess 10 is 90% of the diameter of the emitting surface, and the cavity 17 of the diaphragm 17 is
The diameter of 7 was 60% of the diameter of the emitting surface.

FIG. 3 shows a second embodiment of the present invention. Figure 3
In FIG. 3, reference numeral 31 denotes a ring (piezoelectric ceramic laminate) made of lead zircon titanate-based piezoelectric ceramics polarized in the thickness direction, and adjacent rings 31 are arranged so that their polarization directions are opposite to each other. 31 is electrically connected in parallel.

Reference numeral 36 is a piezoelectric ceramic disc (piezoelectric thin plate ceramic) made of lead zircon titanate-based piezoelectric ceramics polarized in the thickness direction, and the phase of the driving voltage is 180.
The piezoelectric ceramic ring 31 is connected in parallel via a phase shifter 39 for shifting the degree.

Reference numerals 32 and 33 denote metal masses, which form a rear mass and a front mass, respectively. The bolt 34 is made of steel and applies a static compression bias to the piezoelectric ceramic ring 31. Reference numeral 37 is a diaphragm made of an aluminum alloy and having a disk-shaped cavity 377 therein.
Is firmly fixed with an epoxy-based strong adhesive to form the bending vibration body 35. 38 is a plate outside the cavity 377.

The front mass 33 and the flexural vibration body 35 in the recess 10 thereof are fixed by bolts 311 via a ring 310 made of uneven steel. As a result, the bending vibration body 3
The supporting condition of No. 5 is fixed to the periphery, and the flexural vibration frequency of the flexural vibration body 35 can be made lower than that of the peripheral fixation surrounded by the front mass as shown in FIG. The diameter of the ring 310 is 90% of the diameter of the radiating surface, and 37 cavities 377 of the vibration plate
The diameter of the portion was 60% of the diameter of the emitting surface.

[0040]

The first effect of the present invention is that the lower limit frequency of the bandwidth can be made lower than the longitudinal vibration resonance frequency of the Langevin type transducer and the frequency can be lowered.

The reason is that the bending vibration resonance frequency of the bending vibration body provided with the piezoelectric thin plate ceramic and the vibration plate having the cavity inside is attached to the front mass, and the bending vibration resonance frequency is higher than the longitudinal vibration resonance frequency of the Langevin type transducer. This is because the low frequency allows the bandwidth to be expanded to the low frequency region without increasing the size of the transducer.

The second effect is that the bandwidth can be increased as compared with the conventional case.

The reason is that the transducer according to the present invention has three vibration modes, and the bending vibration body in which the piezoelectric thin plate ceramic and the vibration plate having a cavity inside are bonded in order of increasing frequency is bent. There are a vibration mode, a longitudinal vibration mode of a Langevin type transducer, and a bending vibration mode of a plate outside a cavity of a diaphragm having a cavity inside. The longitudinal vibration fundamental resonance mode of the Langevin type oscillator is set so that the bending vibration mode of the entire bending vibration body and the bending vibration mode of the plate outside the cavity of the vibration plate constituting the bending vibration body have mutually opposite phases. Since it is set, the three vibration modes are combined, and the bandwidth can be significantly widened.

[Brief description of drawings]

FIG. 1 is a schematic cross-sectional view of a wave transceiver according to the present invention.

FIG. 2 is an explanatory diagram showing a vibration mode of the wave transceiver according to the present invention.

FIG. 3 is a schematic cross-sectional view showing another example of the wave transceiver according to the present invention.

FIG. 4 is a schematic cross-sectional view showing an example of a conventional wave transceiver.

[Explanation of symbols]

1, 11, 31 Piezoelectric ceramic laminate (ring) 2, 12, 32 Rear mass (metal mass) 3, 13, 33 Front mass (metal mass) 4, 14, 34 Bolt 5 Bending diaphragm 10 Recessed portion 15, 35 Bending vibration Body 16, 36 Piezoelectric ceramic thin plate (piezoelectric ceramic disk) 17, 37 Vibration plate 177, 377 Cavity 18, 38 Plate 19, 39 Phase shifter

─────────────────────────────────────────────────── ─── Continuation of the front page (58) Fields surveyed (Int.Cl. ⁷ , DB name) H04R 17/10 330 H04R 1/44 330

Claims (7)

(57) [Claims] 1. A piezoelectric ceramic laminated body having an internal through hole is arranged between a front mass and a rear mass, and a bolt for applying a compressive stress to the piezoelectric ceramic laminated body is provided through a through hole provided in the piezoelectric ceramic laminated body. In an ultrasonic transducer including a bolted Langevin type vibrator provided, a concave portion is provided on the front surface of the front mass, and a flexural vibrating body in which a piezoelectric thin plate ceramic and a diaphragm having a cavity inside are bonded to each other An ultrasonic wave transmitter / receiver, characterized in that the thin plate ceramic is provided so as to be inside the recessed part, and is floated from the bottom of the recessed part of the front mass. 2. The inner diameter of the concave portion of the front mass is set to 80% or more of the total diameter of the front mass, and the diameter of the cavity of the diaphragm is set to about 50% to 70% of the total diameter of the front mass. The ultrasonic wave transmitter / receiver according to claim 1. 3. A piezoelectric thin plate ceramic is driven so that the bending vibration modes of the entire bending vibration body provided in the recess of the front mass are in opposite phases to the longitudinal vibration fundamental resonance mode of the bolted Langevin type vibrator. The structural dimensions are set such that the voltage phase is shifted, and the bending vibration resonance frequency of the entire bending vibration body is lower than the longitudinal vibration resonance frequency of the bolted Langevin type vibrator. The ultrasonic wave transmitter / receiver according to claim 1. 4. A longitudinal vibration fundamental resonance mode of a bolted Langevin type oscillator is opposite to a bending vibration mode of a plate outside a cavity of a vibration plate constituting a bending vibration body provided in a recess of a front mass. So that
4. The structural dimension is set so that the flexural vibration resonance frequency of the plate outside the cavity of the vibration plate is higher than the longitudinal vibration resonance frequency of the bolted Langevin type vibrator. The ultrasonic transmitter / receiver according to any one of 1. 5. A vibration for vibrating a bending vibration body provided in a concave portion of the front mass of an ultrasonic transducer including a Langevin type vibrator for bolting a front mass and a rear mass with a piezoelectric ceramic laminate interposed therebetween. In the control method, the bending vibration body is formed by laminating a vibration plate having a cavity inside and a piezoelectric thin plate ceramic, and the piezoelectric thin plate ceramic is arranged so as to float from the bottom of the recess so that it is inside the recess. The phase of the driving voltage of the piezoelectric thin plate ceramics is shifted and applied so that the bending vibration mode of the entire bending vibration body has a phase opposite to the longitudinal vibration fundamental resonance mode of the Langevin type vibrator. A method for controlling vibration of an ultrasonic wave transmitter / receiver, comprising: 6. The inner diameter of the concave portion of the front mass is set to 80% or more of the total diameter of the front mass, and the diameter of the cavity of the diaphragm is set to about 50% to 70% of the total diameter of the front mass. The vibration control method for an ultrasonic wave transmitter / receiver according to claim 5, characterized in that: 7. The longitudinal vibration fundamental resonance mode of the Langevin type vibrator is set so that the bending vibration modes of the plates outside the cavity of the vibration plate constituting the bending vibration body have mutually opposite phases, The structural dimension is set such that the flexural vibration resonance frequency of the plate outside the cavity of the diaphragm is higher than the longitudinal vibration resonance frequency of the Langevin type vibrator. Alternatively, the vibration control method of the ultrasonic wave transmitter / receiver according to the sixth aspect.