JP2921616B2 - Piezo acoustic device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a piezoelectric acoustic device which uses a piezoelectric element and is used as a receiver for telephones and other telephones.

[0002]

2. Description of the Related Art A conventional piezoelectric acoustic device has a structure as shown in FIGS. That is, the piezoelectric element 6
Is a method in which a piezoelectric film 8 is formed on one surface of a vibration plate 7, and lead wires 9, 1 and 2 are connected to the vibration plate 7 and electrodes provided on the surface of the piezoelectric film 8.
0 are each soldered. The piezoelectric element 6 is housed in a tray-shaped case 1 having a step 2 in the middle of the inner peripheral surface, and the periphery of the diaphragm 7 is supported by the step 2 and a silicone adhesive 5 (see FIG. 6). ) Or the like. Then, the lead wires 9 and 10 are drawn out of the case 1 from recesses formed in the peripheral wall of the case 1. In such a piezoelectric acoustic device, the sound pressure of the generated sound
To adjust the frequency characteristics, a damper is provided on the upper wall of case 1. For example, in a conventional piezoelectric acoustic device, 20
In the case of using the piezoelectric elements 6 around φ, a through hole 3 of about 1 to 2φ is provided at the center of the upper surface of the case 1, and a Tetron mesh 4 of about # 380 is stretched here to constitute a damper. With this damper, the sound pressure-frequency characteristic is adjusted so that a required sound pressure level is obtained in a predetermined sound range.

[0004]

However, in the conventional piezoelectric acoustic device in which the mesh 4 is stretched in the through hole 3 to constitute a damper, the mesh 4 cut into small pieces is cut into the through hole 3 in the inner wall of the upper wall of the case 1. There is a problem that a fine operation of attaching the adhesive to the periphery is required, and a lot of trouble is required for a process for forming the damper.
In particular, with the miniaturization of mobile phones and cordless horns, this type of piezoelectric acoustic device has been further miniaturized, and the diameter of the piezoelectric element 6 used has been gradually reduced. For this reason, the diameter of the through hole 3 gradually becomes smaller, and the mesh 4
The work of putting up is taking more trouble. Further, as the diameter of the piezoelectric element 6 becomes smaller, it becomes more difficult to obtain a required sound pressure in a predetermined sound range.
Insufficient sound pressure in the low-frequency range near z is a problem.

In view of the above-mentioned problems of the conventional piezoelectric acoustic device, the present invention makes it possible to easily construct a damper, obtain a high sound pressure even in a low-frequency range, and obtain a flat sound pressure-frequency characteristic over the entire range of use. It is an object of the present invention to provide a piezoelectric acoustic device capable of obtaining the following.

[0006]

That is, according to the present invention, in order to achieve the above object, the piezoelectric film 1 is formed on the main surface of the diaphragm 17.
8 and a case 11 having a tray shape with one side open and having a damper on the upper wall. The case 11 accommodates the piezoelectric element 16 and In a piezoelectric acoustic device in which the peripheral portion of the vibration plate 17 is supported and fixed by the inner peripheral wall of the case 11, the damper penetrates a plurality of holes 15 formed in the upper wall of the case 11 and into the holes 15. A piezoelectric acoustic device comprising a small hole having a smaller diameter is provided. The small holes 14 preferably have a diameter of 0.5φ or less, and four or more small holes 14 are preferably provided near the center of the upper wall of the case 1.

[0007]

In the piezoelectric acoustic device according to the present invention, the damper has a plurality of holes 15 formed in the upper wall of the case 11 and
When the case 11 is molded, the hole 15 and the small hole 14 are provided in advance, or the case 11 is formed. later,
The damper can be formed by simply forming the hole 15 and the small hole 14 on the upper surface, and it is unnecessary to attach a complicated mesh at all. In addition, a piezoelectric acoustic device having such a damper can obtain a relatively high sound pressure, particularly in a low-frequency range around 300 Hz, as is clear from the results of tests described later. As a result, a flat sound pressure-frequency characteristic can be obtained over the entire used sound range. In particular, the damper is
A plurality of holes 15 and a smaller diameter penetrating into the holes 15
Because of the small holes 14, the relatively large holes 15
Pressure, and this is applied to the case 1 through the smaller hole 14.
The sound of low frequency is easily released because the sound pressure is released outside
can get. If the diameter of the small holes 14 is 0.5φ or less and the number is 4 or more, better sound pressure-frequency characteristics can be obtained.

[0008]

Next, an embodiment of the present invention will be described in detail with reference to the drawings. 1 to 3 show an embodiment of the present invention. The case 11 for accommodating and supporting the piezoelectric element 16 is formed of a resin in the shape of an inverted tray having an open bottom surface, and has a height approximately halfway along the entire inner circumference of the peripheral wall. A step 12 is formed. Also, the case 11 is opened so that a part of the peripheral wall of the case 11 is opened.
A concave portion 13 is formed from the outer periphery of the upper surface to the inner periphery of the step portion 12.

Further, a plurality of small holes 14 forming a damper are formed in the center of the upper surface of the case 11. FIG.
3, a plurality of large holes 15 having a diameter of about 1φ that are not penetrated to the front side are provided on the inner side of the upper surface of the case 1, and a small hole 14 having a small diameter that passes through to the front side is provided at the center thereof. Has been drilled. The diameter of the small hole 14 is preferably 0.5φ or less, more preferably 0.2φ or less.
The number of small holes 14 having a sufficiently small diameter is preferably four or more, more preferably eight or more. This is because, as the diameter of the small holes 14 increases, the sound pressure level generally decreases.
This is because the sound pressure level decreases on the low frequency sound range side near z. Such a case 1 can be made, for example, by injection molding a resin. At this time, the small hole 1
Although it is preferable to form the holes 4 at the same time, the small holes 14 may be formed by machining after the case 11 is formed.

The piezoelectric element 16 includes a piezoelectric film 18 having electrode layers on both main surfaces of a piezoelectric ceramic, and a metal vibration plate 17.
The vibration plate 17 and the piezoelectric film 18
The lead wires 19 and 20 are soldered to the electrode layer on the surface of the substrate. This piezoelectric element 16 is, as shown in FIG.
While being housed in the case 11, the peripheral portion of the diaphragm 17 is applied to the step portion 12 and fixed by an adhesive 21 made of a silicone resin or the like. In this case, the piezoelectric film 18 is mounted so that the piezoelectric film 18 side faces the opposite side to the opening of the case 11, that is, faces upward in FIG. Further, lead wires 19 and 20 respectively connected to the vibration plate 17 and the piezoelectric film 18 are drawn out of the case 11 through the recess 13.

Further, the recess 13 is filled with an elastic member 22 having elasticity such as a silicone adhesive. The elastic member 22 holds the lead wires 19 and 20 in the recess 13 so as not to move. This piezoelectric acoustic device is shown in FIG.
As shown in the figure, the opening side of the case 11 is applied to the inner surface of the housing 31 of the mobile phone or the cordless horn,
The case is attached to the housing 31 by fusing the peripheral end face of the opening of the case by means such as ultrasonic welding.

Next, an example of a longitudinal sectional shape of the small hole 14 will be described with reference to FIG. First, FIG.
(B), on the contrary, a plurality of holes 15 having a large diameter are provided outside the upper surface of the case 1 and the center thereof is provided at the center thereof. , A small hole 14 having a small diameter is formed. Also, in FIG. 3A, the cross-sectional shape of the large-diameter hole 15 is trapezoidal, but in FIG. 3B, the cross-sectional shape of the large hole 15 is semicircular. Further, in FIG. 4C, a hole 15 having a large diameter is used.
This is an example in which a small hole 14 having a small diameter penetrates the front and inner surfaces of the upper surface of the case 11 without forming the same.

FIG. 7 shows an example in which the sound pressure-frequency characteristics of the embodiment of the present invention and the comparative example are actually measured. That is, in the embodiment of the present invention, the small hole 14 as shown in FIG. 1 to FIG. 3 and FIG. Hole 14
Are arranged on two circumferences having different diameters around the center of the upper surface of the case 11, that is, eight are arranged at equal angular intervals in total. Further, in the comparative example, a # 380 tetron mesh 4 is provided in a 1.7φ through hole 3 provided at the center of the upper wall of the case 11. Otherwise, Case 1
The shape, dimensions, shape and dimensions of the piezoelectric element, and the assembly structure thereof were completely the same. Looking at the sound pressure-frequency characteristics measured in this way, it is clear that the piezoelectric acoustic device according to the embodiment of the present invention has a higher overall sound pressure level than the comparative example except for the sound range where the frequency is high. Have been. In particular, it can be seen that the sound pressure level around 300 Hz is not extremely lower than its peak value, and that a flat sound pressure level is obtained over the entire used sound range.

[0014]

As described above, according to the present invention, a damper can be easily constructed, and a higher sound pressure can be obtained even in a low frequency range, and a flat sound pressure can be obtained.
Frequency characteristics can be obtained. This makes it possible to provide a piezoelectric acoustic device that can obtain good sound pressure characteristics at a lower cost.

[Brief description of the drawings]

FIG. 1 is an exploded perspective view of a piezoelectric acoustic device according to an embodiment of the present invention, as viewed from a bottom surface side.

FIG. 2 is a perspective view from the upper surface side of the piezoelectric acoustic device according to the embodiment.

FIG. 3 is a vertical sectional side view showing a state where the piezoelectric acoustic device according to the embodiment is attached to a housing.

FIG. 4 is a longitudinal sectional view of a main part of an upper wall portion of a case of the piezoelectric acoustic device according to the embodiment.

FIG. 5 is an exploded perspective view of a piezoelectric acoustic device showing a conventional example.

FIG. 6 is a perspective view of the conventional piezoelectric acoustic device.

FIG. 7 shows the sound pressure versus the working example of the present invention and its comparative example.
9 is a graph showing an example of actually measuring frequency characteristics.

[Explanation of symbols]

 11 case 14 small hole 15 hole 16 piezoelectric element 17 diaphragm 18 piezoelectric film

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-60-96096 (JP, A) JP-A-61-139200 (JP, A) JP-A 2-21897 (JP, U) JP-A 3-96 44397 (JP, U) (58) Fields investigated (Int. Cl. ⁶ , DB name) H04R 17/00

Claims (3)

(57) [Claims] A piezoelectric film (1) is provided on a main surface of a diaphragm (17).
8) and a case (1) having a tray-like shape with one side open and a damper on the upper wall.
1), and the piezoelectric element (1) is provided in the case (11).
6), and the peripheral portion of the diaphragm (17) of the piezoelectric element (16) is supported by the inner peripheral wall of the case (11).
In the fixed piezoelectric acoustic device, the damper is a plurality of holes (15) formed in the upper wall of the case (11).
Hole (1) penetrating into the hole (15) of
4) A piezoelectric acoustic device comprising: 2. The piezoelectric acoustic device according to claim 1, wherein the diameter of the small hole (14) is 0.5φ or less. 3. The piezoelectric acoustic device according to claim 1, wherein four or more small holes (14) are provided at the center of the upper wall of the case (11).