JPH0526875Y2 - - Google Patents

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to a piezoelectric acoustic transducer that is incorporated into a telephone handset and the like.

<Conventional technology> Conventionally, this type of piezoelectric acoustic transducer is
There is something like the one shown in Figure 2. That is, this piezoelectric acoustic transducer includes a cap-shaped case 1 in which a sound emission hole 2 is formed in the center, and a piezoelectric vibrator 3 formed by bonding a ceramic piezoelectric element 3b to a metal diaphragm 3a.
, a ring-shaped spacer 4 , and an insulating cover 5 that covers the back side of the piezoelectric vibrator 3 via the spacer 4 .
An external terminal 6 led out from the insulating cover 5,
6, and a back cover 7 that covers the back side of the insulating cover 5. A first air chamber 8 is formed between the piezoelectric vibrator 3 and the insulating cover 5, and a second air chamber 9 is formed between the insulating cover 5 and the back cover 7.

<Problems to be solved by the invention> In the conventional piezoelectric acoustic transducer, in order to flatten the frequency characteristics, the first air chamber 8 and the second air chamber 9 are separated by providing a damping hole 10 in the insulating cover 5. In addition, air braking is performed through this braking hole 10. And this brake hole 10
A braking film 11 is attached to the insulating cover 5 by using an adhesive. It's pasted on.

By the way, when attaching such a braking membrane 11, it is necessary to apply a certain tension to it, and if the tension changes, the resulting piezoelectric acoustic transducer will be damaged. The frequency characteristics were to vary.

Furthermore, an adhesive is used to attach the brake membrane 11, but this adhesive also causes some inconvenience. That is, as shown in FIG. 3A, if the amount of adhesive 12 attached is small and the adhesive 12 is attached only to the small area a, the brake membrane 11 will float and air will not pass through. This increases the area and reduces the braking force. Furthermore, as shown in FIG. 3B, if the amount of adhesive 12 is large and adheres to part b over a wide area, the brake film 11 will adhere to the inner surface of the brake hole 10, reducing the air passage area. As a result, the braking force becomes excessive.
As a result, variations in the frequency characteristics of each piezoelectric acoustic transducer occur depending on the amount of adhesive applied.

The present invention has been made in view of the above circumstances, and aims to provide a piezoelectric acoustic transducer that can eliminate variations in frequency characteristics and stabilize frequency characteristics.

<Means for solving the problems> In order to achieve the above purpose, the present invention
The back side of the piezoelectric vibrator is closed with an insulating cover to form an air chamber between the piezoelectric vibrator and the insulating cover, and
A piezoelectric acoustic transducer is formed by forming a braking hole in an insulating cover and covering the back side of the insulating cover with a back cover. The braking body is characterized in that it is fixed between the insulating cover and the back cover by its own elastic force.

<Function> According to the above configuration, by using an adhesive, it is no longer necessary to attach the braking film made of thin cloth to the insulating cover, and the block-shaped braking body can be attached between the insulating cover and the back cover. It becomes possible to close the brake hole by simply press-fitting and positioning the brake hole without using adhesive. In addition,
At this time, the air for air braking performed through the braking hole that communicates the first air chamber and the second air chamber flows through open air bubbles existing inside the braking body, and the flow at this time The vibration of the piezoelectric vibrator is damped by the resistance.

<Example> Hereinafter, an example of the present invention will be described in detail based on the drawings.

FIG. 1 is a longitudinal sectional side view showing the structure of the piezoelectric acoustic transducer according to this embodiment. This piezoelectric acoustic transducer includes a cap-shaped case 1 with a sound emission hole 2 formed in the center, a piezoelectric vibrator 3 made of a ceramic piezoelectric element 3b bonded to a metal diaphragm 3a,
A ring-shaped spacer 4, an insulating cover 5 that covers and closes the back side of the piezoelectric vibrator 3 via the spacer 4, external terminals 6, 6 led out from the insulating cover 5, and the back side of the insulating cover 5. It is equipped with a back cover 7 that covers the sides. And piezoelectric vibrator 3
A first air chamber 8 is formed between the insulation cover 5 and the back cover 5, while a second air chamber 9 is formed between the insulation cover 5 and the back cover 7. The air chamber 9 is communicated with each other via a brake hole 10 formed in the insulating cover 5.
Note that the reference numeral 14 in the figure indicates a spring terminal that contacts the back side electrode of the piezoelectric vibrator 3.

Furthermore, this piezoelectric acoustic transducer is equipped with a block-shaped brake body 13 made of open-cell foamed plastic such as polyurethane or polyethylene, and this brake body 13 is connected to the brake hole 10 of the insulating cover 5.
It is installed in a position that blocks the That is, this brake body 13 is press-fitted between the insulating cover 5 and the back cover 7 by utilizing its own elastic force, and is positioned and arranged so as to close the brake hole 10 and then fixed. ing. At this time, air for air braking performed through the braking hole 10 that communicates the first air chamber 8 and the second air chamber 9 flows through open air bubbles existing inside the braking body 13. Therefore, the vibration of the piezoelectric vibrator 3 is damped by the flow resistance at this time.

By the way, since this brake body 13 is made of open-cell foam plastic, the braking force of this brake body 13 can be easily adjusted by appropriately setting the foaming rate and outer diameter size of the material resin. become. Further, the brake body 13 may be attached in advance to the position corresponding to the brake hole 10 in the back cover 7, and even if the brake body 13 is attached to the back cover 7 by using adhesive, The inconveniences associated with the use of the conventional example do not occur. Furthermore, the shape of the brake body 13 may be made to correspond to the shape of the brake hole 10, and the brake body 13 may be fitted into the brake hole 10 and then fixed.

<Effects of the invention> As explained above, according to the invention, a block-shaped brake body made of open-cell foamed plastic is fixed between the insulating cover and the back cover by its own elastic force to close the brake hole. Therefore, there is no need to attach a damping film made of thin cloth or the like using an adhesive as in the conventional example. Therefore, an excellent effect can be obtained in that variations in frequency characteristics among piezoelectric acoustic transducers due to these factors cannot occur.
Furthermore, there is no need to apply a certain tension to the brake membrane to be attached or to prepare equipment for applying adhesive, which simplifies the installation work of the brake body. Effects will also be obtained.

[Brief explanation of the drawing]

FIG. 1 is a longitudinal sectional side view showing the structure of a piezoelectric acoustic transducer according to an embodiment of the present invention, FIG. 2 is a longitudinal sectional side view showing the structure of a piezoelectric acoustic transducer according to a conventional example, and FIG. B is a vertical side view showing the main structure of the piezoelectric acoustic transducer. 3... Piezoelectric vibrator, 5... Insulating cover, 7...
Back cover, 8...first air chamber, 9...second air chamber, 10...brake hole, 13...brake body.

Claims (1)

[Claims for Utility Model Registration] The back side of the piezoelectric vibrator is closed with an insulating cover to form an air chamber between the piezoelectric vibrator and the insulating cover, and a braking hole is formed in the insulating cover, and the insulating cover A piezoelectric acoustic transducer whose back side is covered with a back cover is provided with a block-shaped brake body made of open-cell foam plastic that closes the brake hole, and this brake body uses its own elastic force to close the brake hole. A piezoelectric acoustic transducer, characterized in that it is fixed between an insulating cover and a back cover.