Patent Application
20140376335
The present invention relates to an oscillation device that oscillates a sonic wave.
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.
[Patent Document 1] Japanese Registered Utility Model No. 3044460
[Patent Document 2] Japanese Unexamined Patent
Publication No. 2005-295339
[Patent Document 3] Japanese Unexamined Utility Model Registration Publication No. S62-14897
[Patent Document 4] Japanese Unexamined Patent Publication No. H09-46793
[Patent Document 5] Japanese Unexamined Patent Publication No. 2007-318997
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.
The above-mentioned objects, other objects, features and advantages will be made clearer from the preferred exemplary embodiments described below, and the following accompanying drawings.
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.
The vibration member 140 has a sheet shape, and is vibrated by a vibration generated from the piezoelectric element 130. In addition, the vibration member 140 adjusts the fundamental resonance frequency of the piezoelectric element 130. It is preferable that the thickness of the vibration member 140 be equal to or greater than 5 μm and equal to or less than 500 μm. In addition, it is preferable that the vibration member 140 have 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 member 140 is 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 member 140 is not particularly limited insofar as it is a material, such as a metal or a resin, having a high elastic modulus for the piezoelectric element 130 made 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 element 130 is formed of, for example, piezoelectric ceramics such as PZT. However, the piezoelectric element 130 may be formed of other piezoelectric materials. The planar shape of the piezoelectric element 130 is smaller than the planar shape of the vibration member 140.
A laminated body of the piezoelectric element 130 and the vibration member 140 is disposed so that the piezoelectric element 130 is turned toward the upper surface side of the support member 110. That is, the oscillation device 100 oscillates sonic waves on the upper surface side of the support member 110. In the present embodiment, the support member 110 includes a cylindrical lateral portion. The inner wall of the lateral portion supports the edge of the vibration member 140.
The bottom face of the support member 110 is blocked. For this reason, a closed space is formed by the vibration member 140 and the support member 110. The closed space is connected to the outside through a through-hole 116 formed on the bottom face of the support member 110. Meanwhile, a portion of the support member 110 in which the bottom face is blocked serves as the second facing portion 114.
In addition, the upper end of the lateral portion of the support member 110 overhangs to the inside. In the present embodiment, such an overhanging portion serves as the first facing portion 112. In addition, terminals 172 and 174 are provided on the outer surface of the lateral portion of the support member 110.
The first spring 152 is a coil spring, and is formed by a conductor made of a metal or the like. One end of the first spring 152 is attached to the first facing portion 112, and the other end thereof is attached to the piezoelectric element 130. One end of at least one first spring 152 is connected to a first interconnect 171. The first interconnect 171 connects the first spring 152 with the terminal 172. That is, in the present embodiment, a surface electrode of the piezoelectric element 130 is connected to the terminal 172 through the first spring 152 and the first interconnect 171.
The second spring 154 is a coil spring, and is formed by a conductor such as a metal or the like. One end of the second spring 154 is attached to the second facing portion 114, and the other end thereof is attached to the vibration member 140. In the example shown in this drawing, the vibration member 140 is formed by a conductor, and serves as a back electrode of the piezoelectric element 130 as well. One end of at least one second spring 154 is connected to a second interconnect 173. The second interconnect 173 connects the second spring 154 with the terminal 174. That is, in the present embodiment, the back side of the piezoelectric element 130 is connected to the terminal 174 through the vibration member 140, the second spring 154, and the second interconnect 173.
Meanwhile, a cone may be fixed onto the upper surface of the piezoelectric element 130 through 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 device 100.
Meanwhile, the layout of the first springs 152 and the second springs 154 is not limited to the examples shown in
In addition, in the present embodiment, the spring constants of the first spring 152 and the second spring 154 are equal to each other. For example, the first spring 152 and the second spring 154 are coil springs which are the same as each other.
Meanwhile, the oscillation device 100 is used, for example, in a state of being arranged in a plurality of arrays. The oscillation device 100 is used as, for example, a parametric speaker. In this case, a modulation signal for a parametric speaker is input to the terminals 172 and 174 of the oscillation device 100. 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 member 140 and the piezoelectric element 130. 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 springs 152 and the second springs 154 overlap 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 spring 152 and the second spring 154 are equal to each other.
In addition, three or more first springs 152 and three or more second springs 154 are provided. For this reason, as compared with a case where the number of first springs 152 and the number of second springs 154 are two or less, respectively, it is possible to suppress the trembling of a normal line of the vibrator constituted by the piezoelectric element 130 and the vibration member 140. Such an effect increases particularly in a case where the first springs 152 and the second springs 154 overlap 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 spring 152 and the second spring 154 are equal to each other.
In addition, in the present embodiment, the first spring 152 and the second spring 154 serve as a portion of an interconnect for inputting a signal to the piezoelectric element 130. For this reason, even when the piezoelectric element 130 moves up and down due to a vibration, it is possible to suppress the deviation of the interconnect from the piezoelectric element 130.
In addition, the first spring 152 can be directly connected to the piezoelectric element 130. Therefore, the length of the interconnect connected to an upper surface electrode of the piezoelectric element 130 can be reduced. In addition, work efficiency is improved as compared with a case where a normal interconnect is connected to the piezoelectric element 130.
In addition, it is possible to regulate the natural frequency of the vibrator constituted by the piezoelectric element 130 and the vibration member 140 by regulating the spring constant of the first spring 152 and the second spring 154.
The piezoelectric element 130 and the vibration member 140 are supported by the support member 110 through an elastic material 120. Specifically, a concave portion is formed on the inner circumferential surface of the support member 110 throughout the circumference thereof, and the elastic material 120 is buried within the concave portion. The elastic material 120 is a material having an elasticity lower than that of the support member 110, for example, a resin. The edge of the vibration member 140 is buried in the elastic material 120.
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 member 140 is held by the elastic material 120 having an elasticity lower than that of the support member 110. Therefore, the amplitude of the vibration member 140 increases.
The spring receiving member 118 is formed of, for example, a metal such as stainless steel, and has a sheet shape. The edge of the spring receiving member 118 is supported on an inner surface a cylindrical lateral portion of the support member 110. The spring receiving member 118 faces the surface of the vibration member 140 which is located on the opposite side to the piezoelectric element 130. The rigidity of the spring receiving member 118 is higher than the rigidity of the vibration member 140. One end of the second spring 154 is attached to the spring receiving member 118. The second interconnect 173 is connected to the spring receiving member 118. That is, in the present embodiment, the second spring 154 is connected to the second interconnect 173 through the spring receiving member 118.
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 member 110 is used, by regulating a position at which the spring receiving member 118 is attached, the lengths of the first spring 152 and the second spring 154 in a state where the piezoelectric element 130 does not vibrate can be made to be equal to each other.
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.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2011-267826 | Dec 2011 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2012/007811 | 12/5/2012 | WO | 00 | 6/4/2014 |
