JP2015032843A - Ultrasonic vibrator - Google Patents

Abstract

PROBLEM TO BE SOLVED: To solve such a problem that when a diaphragm and a metallic cone are connected by an adhesion strut obtained by solidifying an adhesive, variation in the mechanical characteristics of an ultrasonic vibrator cannot be suppressed, and two resonant frequencies occurring when the ultrasonic vibrator vibrates cannot be controlled, and to provide an ultrasonic vibrator which allows for control of two resonant frequencies while suppressing variation of mechanical characteristics.SOLUTION: An ultrasonic vibrator includes a diaphragm constituted to include a sound wave radiation member, a piezoelectric element, and struts of bobbin-shape being bonded to the diaphragm and sound wave radiation member, respectively.

Description

  The present invention relates to an ultrasonic transducer.

  In recent years, research and development of parametric speakers (so-called ultrasonic speakers) having high directivity have been advanced. An acoustic system including a parametric speaker is suitable for use in a noisy situation because sound can be heard toward a target place (spot). An ultrasonic transducer is used for a parametric speaker. In the ultrasonic speaker, a plurality of ultrasonic transducers are arranged in an array. Also, a modulated wave of an audible sound signal modulated using a carrier signal having a frequency that matches the resonance frequency is input to the ultrasonic transducers arranged in an array. As a method for modulating the audible sound signal, for example, FM (Frequency modulation), AM (Amplitude modulation), SSB (Single side band modulation) or the like can be used.

  Patent Document 1 discloses a technique for improving the flatness of frequency characteristics in a speaker in an audible band. Patent Document 2 discloses a technique for adjusting a resonance frequency according to the size of a diaphragm, which is an ultrasonic microphone used in an ultrasonic band. Patent Document 3 discloses a structure that enables a speaker to be thinned using a piezoelectric element used in an audible band. Patent Document 4 discloses a technique for improving an output sound pressure level by using a plurality of piezoelectric elements.

JP 63-263900 A Japanese Patent Laid-Open No. 04-217200 Japanese Utility Model Publication No. 60-024056 Japanese Utility Model Publication No. 01-030996

  Each disclosure of the above prior art document is incorporated herein by reference. The following analysis was made by the present inventors.

  FIG. 7 is a diagram illustrating an example of a cross section of the ultrasonic transducer 200. Referring to FIG. 7, the ultrasonic transducer 200 includes a vibration plate 203 formed by bonding a piezoelectric element 201 and a metal plate 202 with an adhesive. In addition, the vibration plate 203 and the metal cone 205 are bonded to each other by the adhesive support column 204 in order to withstand vibration in the ultrasonic band and to ensure a sufficient gap (clearance) between the vibration plate 203 and the metal cone 205. . The adhesive strut 204 is formed into a cylindrical shape by individualizing a sufficient amount of adhesive, and the adhesive strut 204 itself constitutes one member (see FIGS. 8 and 9).

  Here, at the time of mass production of the ultrasonic vibrator 200 shown in FIGS. 7 to 9, the amount of adhesive forming the adhesive support column 204 and the shape of the adhesive are not uniform, Variations in mechanical properties (stiffness, friction loss) can occur. Considering the influence on the characteristics (sound volume and frequency characteristics) of the ultrasonic vibrator 200, it is desirable that the variation in the mechanical characteristics of the ultrasonic vibrator 200 is minimal. However, in the case where the adhesive support column 204 is formed by an individualized adhesive, the shape thereof is not constant, and the variation in the mechanical characteristics of the ultrasonic transducer 200 increases.

Further, when the adhesive support column 204 is formed by an individualized adhesive, the shape of the adhesive support column 204 is limited, so that control of the resonance frequency of the ultrasonic transducer 200 is limited. In FIG. 10 showing an example of an electromechanical equivalent circuit of the ultrasonic transducer 200, α indicates each component of the vibration plate 203 (the piezoelectric element 201 and the metal plate 202), β indicates the adhesive support 204, and γ indicates each component of the metal cone 205. . In addition, the mass of a component such as the diaphragm 203 is denoted by m, the friction loss is denoted by r, and the stiffness is denoted by s. For example, m _α represents the mass of the diaphragm 203. Further, the driving force of the piezoelectric element 201 is denoted as “G _α ”, and the mechanical vibration displacement of the ultrasonic transducer 200 is denoted as X. The mechanical vibration displacement X is electrically equivalent to the amount of change in electric charge.

なお、式（１）及び（２）の導出の際、接着支柱２０４の質量ｍ_βは、振動板２０３の質量ｍ_αと比較して極めて小さいため、接着支柱２０４はスティフネスｓ_β及び摩擦損失ｒ_βにより表現できると仮定している。式（１）及び（２）はそれぞれ、２階の常微分方程式であるから、特性方程式を導出することで、正の周波数領域に２つの固有周波数が存在することが明らかである。このことは、超音波振動子２００の電気コンダクタンスの一例を示す図１１からも理解できる。 The equivalent circuit shown in FIG. 10 can be described as two ordinary differential equations as in the following formulas (1) and (2).

Note that when deriving the formulas (1) and (2), the mass m _β of the adhesive strut 204 is extremely small compared to the mass m _{α of the} diaphragm 203, and therefore the adhesive strut 204 has a stiffness s _β and a friction loss r. It is assumed that it can be expressed by _β . Since Equations (1) and (2) are second-order ordinary differential equations, it is clear that there are two natural frequencies in the positive frequency region by deriving the characteristic equation. This can also be understood from FIG. 11 showing an example of the electrical conductance of the ultrasonic transducer 200.

Further, in (1) and (2), assuming that the excitation force and vibration of the ultrasonic transducer 200 are sine waves, the resonance frequencies ω ₁ and ω ₂ are calculated from the equations (1) and (2). (3) and (4).

Referring to Equations (3) and (4), it can be seen that the resonance frequency ω ₂ changes according to the stiffness s _β of the adhesive strut 204, and the two resonance frequencies are closer as the stiffness s _β is smaller.

  In addition, as described above, a considerable amount of adhesive is required to form the adhesive struts 204 in order to withstand vibrations in the ultrasonic band and to ensure a sufficient clearance between the diaphragm 203 and the metal cone 205. is there. That is, the amount of the adhesive that forms the adhesive support column 204 cannot be less than a predetermined amount. If the amount of the adhesive to be used is limited, the difference (gap) or ratio between the two resonance frequencies cannot be set freely. Since the difference or ratio between the two resonance frequencies characterizes the characteristics (sound volume and frequency characteristics) of the sound wave emitted by the ultrasonic transducer 200, the two resonance frequencies cannot be flexibly controlled (difference between the two resonance frequencies). If the ratio cannot be set freely), the degree of freedom in designing the ultrasonic transducer 200 is hindered.

  In view of the above, an object of the present invention is to provide an ultrasonic transducer that contributes to enabling control of two resonance frequencies while suppressing variations in mechanical characteristics.

  According to a first aspect of the present invention, a sound wave radiating member, a diaphragm configured to include a piezoelectric element, and a bobbin-shaped column bonded to each of the vibration plate and the sound wave radiating member, An ultrasonic transducer is provided.

  According to one aspect of the present invention, an ultrasonic transducer that contributes to enabling control of two resonance frequencies while suppressing variation in mechanical characteristics is provided.

It is a figure for demonstrating the outline | summary of one Embodiment. It is a figure which shows an example of the cross section of the ultrasonic transducer | vibrator 10 which concerns on 1st Embodiment. 1 is an example of a three-dimensional view of an ultrasonic transducer 10. It is an example of the exploded view of the ultrasonic transducer | vibrator 10 shown in FIG. 4 is another example of a three-dimensional view of the ultrasonic transducer 10. It is another example of the exploded view of the ultrasonic transducer | vibrator 10 shown in FIG. 2 is a diagram illustrating an example of a cross section of an ultrasonic transducer 200. FIG. 3 is an example of a three-dimensional view of an ultrasonic transducer 200. FIG. It is an example of the exploded view of the ultrasonic transducer | vibrator 200 shown in FIG. 3 is a diagram illustrating an example of an electromechanical equivalent circuit of an ultrasonic transducer 200. FIG. 6 is a diagram illustrating an example of an actual measurement value of electric conductance of an ultrasonic transducer 200. FIG.

  First, an outline of an embodiment will be described with reference to FIG. Note that the reference numerals of the drawings attached to the outline are attached to the respective elements for convenience as an example for facilitating understanding, and the description of the outline is not intended to be any limitation.

  As described above, if the diaphragm and the metal cone are connected by the adhesive support obtained by solidifying the adhesive, variations in the mechanical characteristics of the ultrasonic vibrator cannot be suppressed, and the ultrasonic vibrator vibrates. It is impossible to control the two resonance frequencies generated when Therefore, an ultrasonic transducer that contributes to enabling control of two resonance frequencies while suppressing variations in mechanical characteristics is desired.

  Therefore, as an example, the ultrasonic transducer 100 shown in FIG. 1 is provided. The ultrasonic transducer 100 includes a sound wave radiating member 101, a vibration plate 102 including a piezoelectric element, and a bobbin-shaped column 103 bonded to each of the vibration plate 102 and the sound wave radiation member 101. .

  The ultrasonic transducer 100 connects the vibration plate 102 and the sound wave emitting member 101 using, for example, a support column 103 mainly made of resin or metal instead of the adhesive support column obtained by solidifying the adhesive. Further, by making the shape of the support column 103 into a bobbin shape, a sufficient area of the bonding surface with the vibration plate 102 and the sound wave radiating member 101 is secured, and a necessary bonding strength is given. Furthermore, by changing the diameter of the column portion of the column 103, the stiffness of the column 103 is changed, and the difference or ratio between the two resonance frequencies can be controlled.

  Hereinafter, specific embodiments will be described in more detail with reference to the drawings.

[First Embodiment]
The first embodiment will be described in more detail with reference to the drawings.

  FIG. 2 is a diagram illustrating an example of a cross section of the ultrasonic transducer 10 according to the first embodiment. Referring to FIG. 2, the ultrasonic transducer 10 includes a vibration plate 13 obtained by bonding a piezoelectric element 11 and a metal plate 12 with an adhesive. In addition, since the thickness of the adhesive agent which adhere | attaches the piezoelectric element 11 and the metal plate 12 is very thin, and the quantity used is also a trace amount, illustration is abbreviate | omitted.

  The diaphragm 13 is fixed to the frame 17 via an elastic material 16. An electric signal is input to the ultrasonic transducer 10 through a terminal 18. Sound waves are mainly emitted from the metal cone 15. That is, the metal cone 15 corresponds to the above-described sound wave radiating member 101.

  The piezoelectric element 11 is an element that generates a vibration amplitude using the electrostrictive effect of piezoelectricity. The piezoelectric element 11 has a structure in which a piezoelectric ceramic (not shown) is sandwiched between two electrodes (not shown). As the piezoelectric ceramic, for example, PZT (lead zirconate titanate) can be used. Of course, various piezoelectric elements such as various piezoelectric ceramics can be selected and used as necessary.

  Examples of the metal material used for the metal plate 12 and the metal cone 15 include phosphor bronze, stainless steel, magnesium, aluminum, titanium, beryllium, and alloys thereof.

  For the elastic material 16, for example, an elastic material such as urethane rubber or nitrile rubber can be used. For the frame 17, for example, a resin material, brass, stainless steel, or the like can be used.

  One of the differences between the ultrasonic transducer 10 and the ultrasonic transducer 200 according to the first embodiment is that the vibrating plate 13 and the metal cone 15 are connected by a column 14 instead of the adhesive column 204.

  The support | pillar 14 is not a member obtained by making resin or a metal a main material, and individualizing an adhesive like the adhesion | attachment support | pillar 204. FIG. That is, unlike the adhesive strut 204, it is not obtained by individualizing the adhesive in the manufacturing process of the ultrasonic vibrator, so that the variation in the mechanical characteristics of the strut 14 is suppressed. Moreover, the support | pillar 14 has a bobbin type shape which consists of a disk-shaped adhesion surface and the support | pillar part which connects an adhesion surface.

  FIG. 3 is an example of a three-dimensional view of the ultrasonic transducer 10. FIG. 4 is an example of an exploded view of the ultrasonic transducer 10 shown in FIG. 3 and 4, only the diaphragm 13 (piezoelectric element 11 and metal plate 12), the support column 14 and the metal cone 15 are illustrated.

  The adhesion surface of the support column 14 has a shape and size suitable for the shape of the object to be adhered so that the adhesion strength between the vibration plate 13 and the metal cone 15 is sufficient. Specifically, the adhesive surface of the support column 14 with the diaphragm 13 has a flat disk shape, thereby ensuring the adhesive strength with the flat diaphragm 13. On the other hand, the adhesion surface of the support column 14 with the metal cone 15 has a recess in the center portion following the shape of the metal cone 15. Adhesive strength is ensured by adapting the adhesion surface of the support column 14 to the metal cone 15 to match the shape of the metal cone 15.

  Thus, since the shape of the adhesion surface of the support | pillar 14 is adapted to the target object to adhere | attach, sufficient adhesive strength is securable even if the adhesive agent to apply | coat is small. That is, by devising the shape of the adhesion surface between the diaphragm 13 and the metal cone 15 in the support column 14, sufficient adhesion strength is ensured.

  Moreover, by making the support column 14 into a bobbin shape, the diameter of the support column portion that connects the bonding surface of the diaphragm 13 and the metal cone 15 can be freely adjusted (for example, in FIG. It is thinner than the diameter). As described above, if the diameter of the column portion of the column 14 is changed, the stiffness also changes, and the difference (frequency gap) between the two resonance frequencies can be freely adjusted.

従って、支柱１４における支柱部分の径を調整することによりスティフネスｓ_βもまた調整可能であり、結果的に２つの共振周波数の差分や比率が制御できる。つまり、２つの共振周波数の差分又は比率は、支柱１４の支柱部分の径に応じて定まる。あるいは、支柱１４における支柱部分の径は、超音波振動子１０の振動板１３の駆動により金属コーン１５を振動させた際に生じる２つの共振周波数をどのように制御するかに応じて定まるといえる。 For the sake of easy understanding, if it is assumed that the equivalent constants of the metal cone 15 and the diaphragm 13 are substantially the same and all damping is eliminated, the two resonance frequencies ω ₁ , ω ₂ (ω ₁ < The ratio of ω ₂ ) can be derived from the following equation (5).

Therefore, even stiffness s _beta by adjusting the diameter of the strut portion in the pillar 14 also adjustable, can eventually control the difference or ratio of the two resonance frequencies. That is, the difference or ratio between the two resonance frequencies is determined according to the diameter of the column portion of the column 14. Alternatively, it can be said that the diameter of the column portion of the column 14 is determined according to how the two resonance frequencies generated when the metal cone 15 is vibrated by driving the diaphragm 13 of the ultrasonic transducer 10 are controlled. .

  In 1st Embodiment, although demonstrated using the cone-shaped metal cone 15 as a sound wave radiation member, it is not the meaning which limits the shape of a sound wave radiation member. The shape of the sound wave radiating member may be a disk shape as shown in FIGS. In such a case, the adhesion surface of the support column 14 with the sound wave radiating member may be a disk shape.

As described above, in the ultrasonic transducer 10 according to the first embodiment, instead of the adhesive strut obtained by solidifying the adhesive, for example, using the strut 14 mainly made of resin or metal, The diaphragm 13 and the metal cone 15 are connected. Moreover, by making the shape of the support | pillar 14 into a bobbin shape, sufficient area of the adhesion surface with the diaphragm 13 and the metal cone 15 is ensured, and necessary adhesion strength is given. Further, by changing the diameter of the strut portion in the pillar 14, stiffness s _beta is changed struts 14 can be controlled a difference or ratio of the two resonance frequencies.

  Alternatively, if the bonding conditions for forming the adhesive struts 204 of the ultrasonic transducer 200 are not prepared, the ultrasonic transducer 200 may be damaged, but the ultrasonic transducer 10 requires a necessary adhesive. Because of the small amount, the possibility of breakage is greatly reduced.

  Even if the techniques disclosed in Patent Documents 1 to 4 are applied, the control of the difference and ratio of the two resonance frequencies that occur in the ultrasonic band is realized by the support column that connects the diaphragm and the metal cone. I can't. This is because none of the documents discloses a specific shape of the support for the purpose of controlling resonance in the ultrasonic region. On the other hand, in the ultrasonic transducer | vibrator 10 which concerns on 1st Embodiment, control of the difference or ratio of the resonance frequency which expresses two is implement | achieved by the physical conditions of the support | pillar 14, suppressing manufacturing dispersion | variation. Furthermore, in the ultrasonic vibrator 10, based on the view that the bonding is inexpensive when mass production is taken into consideration, the strut 14 is formed into a bobbin shape, so that the vibration plate 13 and the metal are secured while ensuring the necessary bonding strength. Connection of the cone 15 is realized. For this reason, a specially shaped metal cone or diaphragm is unnecessary, and mass production costs can be suppressed.

  The ultrasonic transducer | vibrator 10 which concerns on 1st Embodiment is suitable for the use to the speaker (ultrasonic speaker) mounted in electronic devices, such as a mobile telephone, a smart phone, a portable audio player, a television apparatus, a tablet terminal, a game machine. is there.

  A part or all of the above embodiments can be described as in the following supplementary notes, but is not limited thereto.

[Appendix 1]
The ultrasonic transducer according to the first aspect described above.
[Appendix 2]
The column is
A first adhesive surface that is bonded to the diaphragm and has a shape that conforms to the shape of the adhesive surface of the diaphragm;
A second adhesive surface that is bonded to the sound wave radiating member and has a shape adapted to the shape of the adhesive surface of the sound wave radiating member;
The ultrasonic transducer according to appendix 1, comprising:
[Appendix 3]
The diameter of the column portion connecting the first bonding surface and the second bonding surface of the column is determined based on two resonance frequencies generated when the sound wave radiating member is vibrated by driving the diaphragm. The ultrasonic transducer of appendix 2.
[Appendix 4]
The ultrasonic transducer according to supplementary note 3, wherein a difference or ratio between the two resonance frequencies is determined according to a diameter of the column portion.
[Appendix 5]
The ultrasonic vibrator according to any one of appendices 1 to 4, wherein the support column includes resin or metal as a material.

  Each disclosure of the cited patent documents and the like cited above is incorporated herein by reference. Within the scope of the entire disclosure (including claims) of the present invention, the embodiments and examples can be changed and adjusted based on the basic technical concept. Various disclosed elements (including each element of each claim, each element of each embodiment or example, each element of each drawing, etc.) within the scope of the claims of the present invention, Selection is possible. That is, the present invention of course includes various variations and modifications that could be made by those skilled in the art according to the entire disclosure including the claims and the technical idea. In particular, with respect to the numerical ranges described in this document, any numerical value or small range included in the range should be construed as being specifically described even if there is no specific description.

10, 100, 200 Ultrasonic vibrator 11, 201 Piezoelectric element 12, 202 Metal plate 13, 102, 203 Diaphragm 14, 103 Strut 15, 205 Metal cone 16, 206 Elastic material 17, 207 Frame 18, 208 Terminal 101 Sound wave Radiation member 204 Adhesive strut

Claims (5)

A sound wave radiating member;
A diaphragm configured with a piezoelectric element;
A bobbin-shaped column that is bonded to each of the diaphragm and the sound wave radiating member;
An ultrasonic transducer comprising: The column is
A first adhesive surface that is bonded to the diaphragm and has a shape that conforms to the shape of the adhesive surface of the diaphragm;
A second adhesive surface that is bonded to the sound wave radiating member and has a shape adapted to the shape of the adhesive surface of the sound wave radiating member;
The ultrasonic transducer according to claim 1, comprising:   The diameter of the column portion connecting the first bonding surface and the second bonding surface of the column is determined based on two resonance frequencies generated when the sound wave radiating member is vibrated by driving the diaphragm. The ultrasonic transducer according to claim 2.   The ultrasonic transducer according to claim 3, wherein a difference or a ratio between the two resonance frequencies is determined according to a diameter of the column portion.   The ultrasonic vibrator according to claim 1, wherein the support column includes a resin or a metal as a material.

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