JP2008060648A - Ultrasonic vibrator - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an ultrasonic vibrator in which output sound pressure is enhanced while suppressing generation of unnecessary noise vibration components or deterioration in durability due to deformation fatigue of a member. <P>SOLUTION: First and second piezoelectric vibrators are arranged to be laminated on the substantially same axis through an intermediate supporting member while spaced apart from each other, the substantially annular intermediate supporting member is arranged on the outer edge of the first piezoelectric vibrator arranged on the underside, the second piezoelectric vibrator is bonded fixedly to the upper portion of the intermediate supporting member, and the first piezoelectric vibrator is secured by a column at the substantially central part of a diaphragm. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an ultrasonic vibrator having a structure in which a piezoelectric plate material polarized in the thickness direction is bonded to a vibration plate and ultrasonic waves are emitted by flexural vibration of the piezoelectric vibrator. The present invention relates to an ultrasonic transducer having an improved arrangement structure of piezoelectric transducers for the purpose of improvement.

  In recent years, progress in the industrial field using ultrasonic technology has been remarkable, and under such a background, there is an increasing demand for higher sound pressure for ultrasonic transducers.

First, the configuration of a conventional ultrasonic transducer will be described. FIG. 3 is a cross-sectional view showing a configuration of a conventional ultrasonic transducer.
The conventional ultrasonic transducer 22 shown in FIG. 3 is a mortar-shaped resonator that is a portion that emits ultrasonic waves at a substantially central portion of the upper surface of the piezoelectric transducer 3c obtained by bonding the piezoelectric plate material 1c and the diaphragm 2c. 4 is fixed by an epoxy-based adhesive 5 and the piezoelectric vibrator 3c is supported and bonded to a ring-shaped support base 9 by a low-elastic adhesive 8 (for example, Patent Documents). 1).

  Here, when an AC voltage is applied to the thin film electrodes formed on both main surfaces of the piezoelectric plate material 1c, the piezoelectric plate material 1c expands and contracts in the longitudinal direction, and the piezoelectric vibrator 3c is supported by the expansion and contraction motion. Bending vibration as shown by a dotted line in the figure is caused with a portion bonded to the base 9 as a node. At this time, the bowl-shaped resonator 4 is fixed to a portion corresponding to the abdominal part of the bending motion, so that the whole causes a vertical piston motion, and as a result, ultrasonic waves are emitted from the resonator 4. Will be done.

  If this ultrasonic transducer 22 remains as it is, the output sound pressure of the ultrasonic wave depends only on the vertical amplitude of the resonator 4, that is, the degree of deformation of the bending motion of the piezoelectric vibrator 3c, so that a large output sound pressure is realized. There is a problem that things are difficult.

  Therefore, a means of replacing the piezoelectric plate material 1c of the ultrasonic transducer 22 with a laminated piezoelectric plate material can be considered. If such a means is used, the piezoelectric distortion effect of the piezoelectric plate material is increased by the lamination, and the degree of deformation of the bending motion of the piezoelectric vibrator 3c is increased while maintaining the same voltage applied to the piezoelectric plate material 1c. Therefore, it is possible to increase the vertical amplitude of the resonator 4 and improve the output sound pressure.

JP-A-5-292597 (page 3, FIG. 1)

  When the ultrasonic vibrator is configured as described above, the electrical capacity when driven at a relatively high frequency such as in the ultrasonic region is affected by the increase in electric capacity depending on the lamination and thinning of the piezoelectric plate material. A new problem occurs that the resistance value is significantly reduced and the power consumption is remarkably increased.

  Further, even if the power consumption is within an allowable range, the piezoelectric plate member 1c and the vibration plate 2c constituting the piezoelectric vibrator 3c are accompanied by an increase in the degree of bending deformation of the piezoelectric vibrator 3c. The distortion rate increases.

This phenomenon will be described with reference to the drawings. FIG. 4 is a diagram showing a stress-strain curve of a material used in a conventional ultrasonic transducer, in which the vertical axis represents the material stress and the horizontal axis represents the material strain rate.
As shown in the stress-strain rate curve of FIG. 4, the strain rate exceeds the linear elastic region and enters the nonlinear region. This means that the ultrasonic transducer does not perform so-called elastic vibration, which is premised on driving within the strain rate of the linear elastic region, and is caused by generation of unnecessary noise vibration components and deformation fatigue of members. This leads to a new problem of reduced durability.

  Therefore, the present invention solves the above-described problems, and an ultrasonic transducer with improved output sound pressure while suppressing generation of unnecessary noise vibration components and deterioration in durability due to deformation fatigue of members. The purpose is to provide.

  In order to achieve the above object, the ultrasonic transducer of the present invention adopts the following configuration.

  The ultrasonic vibrator according to the present invention includes a first piezoelectric vibrator formed by laminating a first piezoelectric plate material having thin film electrodes formed on both main surfaces thereof on one side or both sides of the first diaphragm, and the first piezoelectric vibrator. An annular intermediate support member that abuts and fixes the lower surface on the outer edge of one main surface of one piezoelectric vibrator, and a substantially central portion of the other main surface of the first piezoelectric vibrator as a base A second piezoelectric plate material with thin film electrodes formed on both main surfaces is fixed on one or both sides of the second diaphragm, which is fixed to the upper surface of the supporting pillar and the annular intermediate support member. And a second piezoelectric vibrator formed together.

  Furthermore, the ultrasonic transducer of the present invention is fixedly arranged with the total mass of the second piezoelectric transducer in the inner region from the location where the second piezoelectric transducer is fixedly arranged by the annular intermediate support member. The annular intermediate support member and the second piezoelectric vibrator are arranged so that the total mass of the second piezoelectric vibrator in the outer peripheral region in the outer peripheral region is substantially equal to the location.

  Furthermore, the ultrasonic transducer of the present invention is characterized in that the annular intermediate support member and the second piezoelectric transducer are fixed in a line contact state.

  Furthermore, the ultrasonic transducer of the present invention is characterized in that a mortar-shaped resonator is fixed on the upper surface of the central portion of the second piezoelectric transducer.

  In the ultrasonic vibrator according to the present invention, by adopting the configuration as described above, the bending deformation degree of the piezoelectric vibrator is kept within the linear elastic region of the diaphragm and the piezoelectric plate material constituting the piezoelectric vibrator. A large vibration amplitude of vertical vibration can be realized. As a result, it is possible to radiate an ultrasonic wave with a large output sound pressure while suppressing the generation of unnecessary noise vibration components and maintaining the durability of the member as compared with the conventional ultrasonic vibrator.

  Hereinafter, the configuration and drive mechanism of the ultrasonic transducer in the embodiment of the present invention will be described. In addition, the same part in the structure of this invention is demonstrated using a same sign as a background art.

First, a configuration example of the ultrasonic transducer in the present invention will be described. FIG. 1 is a cross-sectional view showing a configuration example of an ultrasonic transducer according to the present invention.
As shown in the sectional view of FIG. 1, the ultrasonic vibrator 21 in the embodiment of the present invention includes a first piezoelectric vibrator 3a formed by bonding a piezoelectric plate material 1a and a vibrating plate 2a, and a piezoelectric plate material in the same manner. A second piezoelectric vibrator 3b formed by laminating 1b and a diaphragm 2b, a resonator 4 bonded and fixed to the upper surface of a substantially central portion of the second piezoelectric vibrator 3b with an adhesive 5, and a first piezoelectric vibrator A support 6 for fixing 3a, and an intermediate support member 7 for transmitting vibration from the first piezoelectric vibrator 3a to the second piezoelectric vibrator 3b. The first piezoelectric vibrator 3a is strongly fixed to the support 6 on the lower surface side of the substantially central portion of the diaphragm 2a, and the second piezoelectric vibrator 3b is the diaphragm 2a in the first piezoelectric vibrator 3a. An elastic adhesive 8 is bonded and fixed on a substantially ring-shaped intermediate support member 7 provided on the upper surface of the outer edge. Further, the support 6 shown in the figure is fixed to a base (not shown).

  Here, the position where the second piezoelectric vibrator 3b is bonded and fixed by the intermediate support member 7 is based on the total mass of the second piezoelectric vibrator 3b on the center side of the position where the second piezoelectric vibrator 3b is bonded and fixed and the position where the second piezoelectric vibrator 3b is bonded and fixed Also, it is desirable that the total mass of the second piezoelectric vibrator 3b on the outer peripheral side be a portion where the mass is substantially equal. Further, in the intermediate support member 7, it is desirable that a portion of the intermediate support member 7 that contacts the second piezoelectric vibrator 3 b has a sharp and sharp cross-sectional shape so that the mutual contact area is a minimum line contact. .

  The reason will be described below. In the configuration as described above, when an AC voltage having an ultrasonic frequency is applied to thin film electrodes (not shown) formed on both surfaces of the piezoelectric plate materials 1a and 1b, the piezoelectric effect in the radial direction of the piezoelectric plate materials 1a and 1b is increased. The first and second piezoelectric vibrators 3a and 3b cause bending vibration in the vertical direction. At this time, the polarization directions of the piezoelectric plates 1a and 1b and the phase of the AC voltage applied thereto are set so that the bending deformation directions of the first and second piezoelectric vibrators 3a and 3b are opposite to each other. Therefore, as shown in FIG. 2, when the lower first piezoelectric vibrator 3a is convex downward, the upper second piezoelectric vibrator 3b is convex upward (FIG. 2A). On the contrary, when the lower first piezoelectric vibrator 3a is convex upward, the upper second piezoelectric vibrator 3b is convex downward (see FIG. 2B). Will have.

  By having such a vibration mode, the first piezoelectric vibrator 3a has the maximum vibration amplitude at the outer edge with the portion fixed by the support column 6 as a fulcrum, and the intermediate support member 7 is moved by the outer edge. Thus, the second piezoelectric vibrator 3b bonded and fixed thereon is vibrated. Here, the place where the second piezoelectric vibrator 3b is supported and fixed by the intermediate support member 7 is the place where the total mass of the second piezoelectric vibrator 3b inside and outside the place is substantially equal to each other as described above. As a result, the second piezoelectric vibrator 3b causes bending vibration in such a manner that the portion is a node. That is, the amplitude of the flexural vibration of the second piezoelectric vibrator 3b itself at this location is zero.

  Then, since the excitation force from the first piezoelectric vibrator 3a is transmitted to the entire second piezoelectric vibrator 3b at the node portion where the amplitude of the flexural vibration becomes zero, the excitation force is transmitted to the second piezoelectric vibrator 3b. The influence on the bending vibration itself of the piezoelectric vibrator 3b is reduced. Therefore, the upper and lower vibration amplitudes at the outer edge portion of the first piezoelectric vibrator 3a can be transmitted to the entire second piezoelectric vibrator 3b while maintaining substantially the same amplitude.

  By the drive mechanism as described above, the ultrasonic vibrator 21 according to the present invention has the first piezoelectric vibration in addition to the amplitude of the flexural vibration of the second piezoelectric vibrator 3b itself as shown in the vibration mode of FIG. Due to the overlap of the amplitude of vertical vibration by the element 3a, the resonator 4 placed and bonded to the upper surface of the second piezoelectric vibrator 3b is larger than when the second piezoelectric vibrator 3b is driven alone. It becomes possible to vibrate up and down with the amplitude amount. As a result, it is possible to emit ultrasonic waves with higher output sound pressure as compared with the conventional ultrasonic vibrator 22 (see FIG. 3) that is driven only by the bending vibration of the piezoelectric vibrator.

Further, in this ultrasonic vibrator 21, the contact area between the second piezoelectric vibrator 3b and the central support member 7 is reduced as much as possible because the cross-sectional shape of the central support member 7 is sharp and sharp. ing. Therefore, it is possible not only to suppress unnecessary noise vibration components caused by contact between the vibrating bodies of the first and second piezoelectric vibrators 3a and 3b as much as possible, but also to reduce the interaction of vibrations in both vibrating bodies as much as possible. Therefore, the first and second piezoelectric vibrators 3a and 3b can be driven while maintaining their maximum vibration amplitudes without hindering the vibration performance of each other.

  Further, in the ultrasonic vibrator 21 according to the present invention, as in the conventional ultrasonic vibrator 22 (see FIG. 3) described above, the vertical amplitude of the resonator 4 is replaced without replacing the piezoelectric plate material 1c with the laminated piezoelectric plate material. Therefore, it is not necessary to consider the increase in power consumption due to the lamination and thinning of the piezoelectric plate material, which has been a problem with the ultrasonic vibrator 22 using the laminated piezoelectric plate material.

  In addition, in the conventional ultrasonic vibrator 22 (see FIG. 3), the piezoelectric plate material 1c is replaced with a laminated piezoelectric plate material, so that the degree of bending deformation of the piezoelectric vibrator 3c is increased. The distortion rate of the members of the piezoelectric plate material 1c and the vibration plate 2c constituting the vibrator 3c is increased, and as shown in the stress-strain rate curve (see FIG. 4), the distortion rate is unnecessary due to entering the nonlinear region. Although there was a problem of generation of noise vibration components and deterioration of durability due to deformation fatigue of members, the ultrasonic vibrator 21 according to the present invention in the present invention includes the first and second piezoelectric vibrators 3a and 3b. The degree of bending deformation in the individual members of the piezoelectric plate materials 1a and 1b and the vibration plates 2a and 2b does not increase so much. Therefore, since the distortion rate of each member does not enter the non-linear region as described above, generation of unnecessary noise vibration components is suppressed, and ultrasonic waves with a large output sound pressure are maintained while maintaining the durability of the members. It becomes possible to radiate.

  In this embodiment, in the first and second piezoelectric vibrators 3a and 3b, a configuration example in which one piezoelectric plate material 1a and 1b is arranged on each of the vibration plates 2a and 2b is shown. The configuration is not limited to this, and two piezoelectric plate members may be provided for each of the diaphragms 2a and 2b, and the two piezoelectric vibrators may be of a bimorph type, or only one of the piezoelectric vibrators may be of a bimorph type. Absent.

It is sectional drawing which showed the structural example of the ultrasonic transducer | vibrator of this invention. It is sectional drawing which showed the vibration shape of the ultrasonic transducer | vibrator of this invention. It is sectional drawing which showed the conventional ultrasonic transducer | vibrator. It is the figure which showed the stress-strain curve of the material used for the conventional ultrasonic transducer | vibrator.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1a, 1b Piezoelectric plate material 2a, 2b Diaphragm 3a 1st piezoelectric vibrator 3b 2nd piezoelectric vibrator 4 Resonator 5 Adhesive 6 Support | pillar 7 Intermediate support member 8 Elastic adhesive 9 Support stand

Claims (4)

In an ultrasonic transducer that transmits ultrasonic waves by bending vibration of a piezoelectric transducer,
A first piezoelectric vibrator formed by laminating a first piezoelectric plate material having thin film electrodes formed on both main surfaces thereof on one or both surfaces of the first diaphragm;
An annular intermediate support member that abuts and fixes the lower surface on the outer edge of one main surface of the first piezoelectric vibrator,
A support column that supports and fixes a substantially central portion of the other main surface of the first piezoelectric vibrator to a base;
A second piezoelectric plate member, which is in contact with and fixed to the upper surface of the annular intermediate support member and has a thin film electrode formed on both main surfaces thereof, is bonded to one or both surfaces of the second diaphragm. And an ultrasonic vibrator. The total mass of the second piezoelectric vibrator in the area inside the place where the second piezoelectric vibrator is fixedly arranged by the annular intermediate support member, and the first mass in the outer peripheral area than the place where the second piezoelectric vibrator is fixedly arranged. The superconductor according to claim 1, wherein the annular intermediate support member and the second piezoelectric vibrator are disposed so that a total mass of the two piezoelectric vibrators is substantially equal. Sonic transducer. The ultrasonic vibrator according to claim 1, wherein the annular intermediate support member and the second piezoelectric vibrator are fixed in a line contact state. The ultrasonic vibrator according to any one of claims 1 to 3, wherein a mortar-shaped resonator is fixed to an upper surface of a central portion of the second piezoelectric vibrator.

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