Oscillation device

A vibration member (140) has a sheet shape. A piezoelectric element (130) is attached to one surface of the vibration member (140). A support member (110) supports the edge of the vibration member (140). The support member (110) includes a first facing portion (112) and a second facing portion (114). The first facing portion (112) faces the surface of the vibration member (140) to which the piezoelectric element (130) is attached. The second facing portion (114) faces the surface of the vibration member (140) which is located on the opposite side to the piezoelectric element (130). A first spring (152) is provided between the first facing portion (112) and the vibration member (140) or the piezoelectric element (130). A second spring (154) is provided between the second facing portion (114) and the vibration member (140).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a national stage application of International Application No. PCT/JP2012/007811 entitled “Oscillation Device,” filed on Dec. 5, 2012, which claims the benefit of the priority of Japanese Patent Application No. 2011-267826, filed on Dec. 7, 2011, the disclosures of each of which are hereby incorporated by reference in their entirety.

TECHNICAL FIELD

The present invention relates to an oscillation device that oscillates a sonic wave.

BACKGROUND ART

There is a parametric speaker as one of speakers. For example, as disclosed in Patent Document 1, the parametric speaker modulates an audio signal into a modulation signal of an ultrasonic wave band, and demodulates the modulation signal into an audible sound in the atmosphere.

As an oscillation device that oscillates a sonic wave of an ultrasonic wave band, there is a device in which a piezoelectric element is used as a vibrator (for example, Patent Documents 1 to 4). When a piezoelectric element is used as a vibrator, it is necessary to form electrodes on both sides of the piezoelectric element, and to input a signal between the two electrodes. Patent Documents 1 and 2 of these Patent Documents disclose that a terminal for inputting a signal to the electrode located on the upper surface side of the piezoelectric element utilizes a spring.

Meanwhile, Patent Document 5 discloses that in a piezoelectric actuator, a piezoelectric element is supported by a power feeding support portion through an elastic body.

RELATED DOCUMENT

Patent Document

DISCLOSURE OF THE INVENTION

In a structure disclosed in Patent Documents 1 and 2, a spring is connected to one surface of a vibrator. Since a force from the spring is applied to the surface of the piezoelectric element to which the spring is connected, the balance of stress which is applied to the piezoelectric element is impaired. In this case, the characteristics of the oscillation device deteriorate.

An object of the present invention is to provide an oscillation device capable of satisfactorily maintaining the balance of stress which is applied to a piezoelectric element.

According to the present invention, there is provided an oscillation device including: a sheet-like vibration member; a piezoelectric element which is attached to one surface of the vibration member; a support member that supports an edge of the vibration member; a first facing portion, provided in the support member, which faces the one surface of the vibration member; a second facing portion, provided in the support member, which faces a surface which is located on the opposite side to the one surface of the vibration member; a first spring which is provided between the vibration member or the piezoelectric element and the first facing portion; and a second spring which is provided between the vibration member and the second facing portion.

According to the present invention, it is possible to satisfactorily maintain the balance of stress which is applied to the vibration member and the piezoelectric element.

DESCRIPTION OF EMBODIMENTS

Hereinafter, the embodiments of the present invention will be described with reference to the accompanying drawings. In all the drawings, like elements are referenced by like reference numerals and descriptions thereof will not be repeated.

First Embodiment

FIG. 1is a diagram illustrating a configuration of an oscillation device100according to a first embodiment. The oscillation device100includes a vibration member140, a piezoelectric element130, a support member110, first springs152, and second springs154. The vibration member140has a sheet shape. The piezoelectric element130is attached to one surface of the vibration member140. The support member110supports the edge of the vibration member140. The support member110includes a first facing portion112and a second facing portion114. The first facing portion112faces the surface of the vibration member140to which the piezoelectric element130is attached. The second facing portion114faces the surface of the vibration member140which is located on the opposite side to the piezoelectric element130. The first springs152are provided between the first facing portion112and the vibration member140or the piezoelectric element130. The second springs154are provided between the second facing portion114and the vibration member140. In this embodiment, the springs are attached onto both sides of a vibrator constituted by the vibration member140and the piezoelectric element130. Therefore, it is possible to satisfactorily maintain the balance of stress which is applied to the vibrator. Hereinafter, a detailed description will be given.

The vibration member140has a sheet shape, and is vibrated by a vibration generated from the piezoelectric element130. In addition, the vibration member140adjusts the fundamental resonance frequency of the piezoelectric element130. It is preferable that the thickness of the vibration member140be equal to or greater than 5 μm and equal to or less than 500 μm. In addition, it is preferable that the vibration member140have a modulus of longitudinal elasticity which is an index indicating rigidity being equal to or greater than 1 GPa and equal to or less than 500 GPa. When the rigidity of the vibration member140is excessively low or excessively high, there is the possibility of the characteristics or reliability of a mechanical vibrator being damaged. Meanwhile, a material constituting the vibration member140is not particularly limited insofar as it is a material, such as a metal or a resin, having a high elastic modulus for the piezoelectric element130made of a brittle material, but it is preferable that the material be phosphor bronze, stainless steel or the like from the viewpoint of workability or cost.

The piezoelectric element130is formed of, for example, piezoelectric ceramics such as PZT. However, the piezoelectric element130may be formed of other piezoelectric materials. The planar shape of the piezoelectric element130is smaller than the planar shape of the vibration member140.

A laminated body of the piezoelectric element130and the vibration member140is disposed so that the piezoelectric element130is turned toward the upper surface side of the support member110. That is, the oscillation device100oscillates sonic waves on the upper surface side of the support member110. In the present embodiment, the support member110includes a cylindrical lateral portion. The inner wall of the lateral portion supports the edge of the vibration member140.

The bottom face of the support member110is blocked. For this reason, a closed space is formed by the vibration member140and the support member110. The closed space is connected to the outside through a through-hole116formed on the bottom face of the support member110. Meanwhile, a portion of the support member110in which the bottom face is blocked serves as the second facing portion114.

In addition, the upper end of the lateral portion of the support member110overhangs to the inside. In the present embodiment, such an overhanging portion serves as the first facing portion112. In addition, terminals172and174are provided on the outer surface of the lateral portion of the support member110.

The first spring152is a coil spring, and is formed by a conductor made of a metal or the like. One end of the first spring152is attached to the first facing portion112, and the other end thereof is attached to the piezoelectric element130. One end of at least one first spring152is connected to a first interconnect171. The first interconnect171connects the first spring152with the terminal172. That is, in the present embodiment, a surface electrode of the piezoelectric element130is connected to the terminal172through the first spring152and the first interconnect171.

The second spring154is a coil spring, and is formed by a conductor such as a metal or the like. One end of the second spring154is attached to the second facing portion114, and the other end thereof is attached to the vibration member140. In the example shown in this drawing, the vibration member140is formed by a conductor, and serves as a back electrode of the piezoelectric element130as well. One end of at least one second spring154is connected to a second interconnect173. The second interconnect173connects the second spring154with the terminal174. That is, in the present embodiment, the back side of the piezoelectric element130is connected to the terminal174through the vibration member140, the second spring154, and the second interconnect173.

Meanwhile, a cone may be fixed onto the upper surface of the piezoelectric element130through an adhesive layer. This cone is made of, for example, a metal, and is provided in order to increase an amount of sonic waves which are output by the oscillation device100.

FIG. 2is a plan view illustrating a layout of the first springs152. In the example shown in this drawing, both the piezoelectric element130and the vibration member140have a rectangular shape. Three or more first springs152are provided at positions which do not overlap each other. In the example shown in this drawing, the first springs152are respectively provided on four corners of the piezoelectric element130.

FIG. 3is a plan view illustrating a layout of the second springs154. In the example shown in this drawing, three or more second springs154are provided at positions which do not overlap each other. In the example shown in this drawing, the second springs154are provided at positions overlapping the first springs152when seen in a plan view. Specifically, the second springs are respectively provided at positions overlapping the four corners of the piezoelectric element130.

Meanwhile, the layout of the first springs152and the second springs154is not limited to the examples shown inFIGS. 2 and 3. For example, as shown inFIG. 4, the first springs152may be further provided at portions corresponding to the center of the long side of the piezoelectric element130, in addition to portions shown inFIG. 2. In this case, the second springs154are also provided additionally at positions overlapping the first springs152when seen in a plan view.

In addition, in the present embodiment, the spring constants of the first spring152and the second spring154are equal to each other. For example, the first spring152and the second spring154are coil springs which are the same as each other.

Meanwhile, the oscillation device100is used, for example, in a state of being arranged in a plurality of arrays. The oscillation device100is used as, for example, a parametric speaker. In this case, a modulation signal for a parametric speaker is input to the terminals172and174of the oscillation device100. The modulation signal is generated, for example, by performing amplitude modulation (AM), double side band (DSB) modulation, single side band (SSB) modulation, or frequency modulation (FM) on an audio signal of an audible sound which is input from the outside.

As described above, according to the present embodiment, the springs are attached to both sides of the vibrator constituted by the vibration member140and the piezoelectric element130. Therefore, it is possible to satisfactorily maintain the balance of stress which is applied to the vibrator. Such an effect increases particularly in a case where the first springs152and the second springs154overlap each other when seen in a plan view. In addition, such an effect increases particularly in a case where the spring constants of the first spring152and the second spring154are equal to each other.

In addition, three or more first springs152and three or more second springs154are provided. For this reason, as compared with a case where the number of first springs152and the number of second springs154are two or less, respectively, it is possible to suppress the trembling of a normal line of the vibrator constituted by the piezoelectric element130and the vibration member140. Such an effect increases particularly in a case where the first springs152and the second springs154overlap each other when seen in a plan view. In addition, such an effect increases particularly in a case where the spring constants of the first spring152and the second spring154are equal to each other.

In addition, in the present embodiment, the first spring152and the second spring154serve as a portion of an interconnect for inputting a signal to the piezoelectric element130. For this reason, even when the piezoelectric element130moves up and down due to a vibration, it is possible to suppress the deviation of the interconnect from the piezoelectric element130.

In addition, the first spring152can be directly connected to the piezoelectric element130. Therefore, the length of the interconnect connected to an upper surface electrode of the piezoelectric element130can be reduced. In addition, work efficiency is improved as compared with a case where a normal interconnect is connected to the piezoelectric element130.

In addition, it is possible to regulate the natural frequency of the vibrator constituted by the piezoelectric element130and the vibration member140by regulating the spring constant of the first spring152and the second spring154.

Second Embodiment

FIG. 5is a diagram illustrating a configuration of an oscillation device100according to a second embodiment. The present embodiment has the same configuration as that of the oscillation device100according to the first embodiment, except for the following points.

The piezoelectric element130and the vibration member140are supported by the support member110through an elastic material120. Specifically, a concave portion is formed on the inner circumferential surface of the support member110throughout the circumference thereof, and the elastic material120is buried within the concave portion. The elastic material120is a material having an elasticity lower than that of the support member110, for example, a resin. The edge of the vibration member140is buried in the elastic material120.

In the present embodiment, it is also possible to obtain the same effect as that of the first embodiment. In addition, the edge of the vibration member140is held by the elastic material120having an elasticity lower than that of the support member110. Therefore, the amplitude of the vibration member140increases.

Third Embodiment

FIG. 6is a diagram illustrating a configuration of an oscillation device100according to a third embodiment. The oscillation device100according to the present embodiment has the same configuration as that of the oscillation device100according to the second embodiment, except that the support member110includes a spring receiving member118(second facing portion).

The spring receiving member118is formed of, for example, a metal such as stainless steel, and has a sheet shape. The edge of the spring receiving member118is supported on an inner surface a cylindrical lateral portion of the support member110. The spring receiving member118faces the surface of the vibration member140which is located on the opposite side to the piezoelectric element130. The rigidity of the spring receiving member118is higher than the rigidity of the vibration member140. One end of the second spring154is attached to the spring receiving member118. The second interconnect173is connected to the spring receiving member118. That is, in the present embodiment, the second spring154is connected to the second interconnect173through the spring receiving member118.

In the present embodiment, it is also possible to obtain the same effect as that of the second embodiment. In addition, even when the existing support member110is used, by regulating a position at which the spring receiving member118is attached, the lengths of the first spring152and the second spring154in a state where the piezoelectric element130does not vibrate can be made to be equal to each other.

Fourth Embodiment

FIG. 7is a diagram illustrating a configuration of an oscillation device100according to a fourth embodiment. The oscillation device100according to the present embodiment has the same configuration as that of the oscillation device100according to the third embodiment, except that the first spring152and the second spring154are flat springs (leaf springs).

In the present embodiment, it is also possible to obtain the same effect as that of the third embodiment.

As described above, although the embodiments of the present invention have been set forth with reference to the drawings, these are merely illustrative of the invention, and various configurations other than those stated above can be adopted.

The application claims priority from Japanese Patent Application No. 2011-267826 filed on Dec. 7, 2011, the content of which is incorporated herein by reference in its entirety.