JP3423749B2 - Piezoelectric acoustic transducer - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a piezoelectric acoustic transducer in which a piezoelectric element is mounted inside a housing of a mobile phone, a handset of a so-called cordless phone or the like.

[0002]

2. Description of the Related Art In mobile phones, cordless phones and the like, acoustic transducers using piezoelectric elements are used. The piezoelectric element is generally one in which a piezoelectric film is formed on one or both sides of a diaphragm made of a metal disk, and electrodes are further formed on the surface of this piezoelectric film. Such a piezoelectric element
It is mounted in a case, which is then incorporated inside the housing of the acoustic transducer.

FIG . 5 shows the structure of a conventional general acoustic transducer, in which a sound emitting port 4 is provided in the earpiece of the housing 1, and a cylindrical shape is erected inside the sound emitting port 4. The case support part 2 is formed. The case 3 has an air braking hole 3b at the center of its bottom wall 3a, and a peripheral wall 3c is provided from one surface of the bottom wall 3a around the air braking hole 3b. The piezoelectric element 7 is housed inside the peripheral wall 3a, and the outer peripheral portion of the diaphragm of the piezoelectric element 7 is bonded to the step portion provided on the inner peripheral surface of the peripheral wall 3a. Lead wires 6 connected to the vibration plate and electrodes of the piezoelectric element 7 are drawn out from the case 3, and the lead wires 6 are connected to an electric circuit (not shown) via a connector. A flange 3d is provided on the extension surface of the bottom wall 3a of the case 3 outside the peripheral wall 3c of the case 3, and the flange 3d is fixed to the case support portion 2 with a screw 10.

[0004]

However, this conventional piezoelectric acoustic transducer has the following problems. First, by incorporating the piezoelectric element 7 in the case 3,
Furthermore, by incorporating this case 3 in the housing 1,
Since the piezoelectric element 7 is enclosed between the case 3 and the housing 1, it is not easy to pull out the lead wire 6. Further, when a defect occurs in the piezoelectric element 7, it is necessary to remove the case 3 together with the housing 1 and then replace the piezoelectric element 7. Therefore, the replacement is troublesome. Secondly,
When water enters from the sound output hole 4 of the housing 1, the water comes into contact with the piezoelectric element 7 and a failure due to a short circuit or the like of the piezoelectric element 7 is likely to occur. Third, the air braking hole 3b and the sound output hole 4
Except for the piezoelectric element 7, the case 3 and the housing 1 are not included.
Since it is closed, there is no sound inside the case 1.
In particular, it is impossible to obtain a sufficient sound pressure especially in the low tone range.

The present invention has been made in view of such conventional problems.
Easy replacement of the assembly or a piezoelectric element, failure due to water occur difficulty rather, and an object of the invention to provide a piezoelectric transducer of the sound pressure in the bass region can be secured.

[0006]

That is, according to the present invention,
In order to achieve the above-mentioned purpose, the piezoelectric element 17 is attached to the case 25.
In the piezoelectric acoustic conversion device in which the case 25 is attached inside the housing 11 having the sound emission hole 24, the case 25 has a bottom wall 3 having an air braking hole 16.
1 and a peripheral wall 32 standing upright from the peripheral portion of the bottom wall 31, and the piezoelectric film 19 is formed on one side or both sides of the vibration plate 18.
And said peripheral portion of the piezoelectric element 17 is attached to the inner periphery of the peripheral wall 32 of the case 25, the case 25, with attached to the inside of the housing 11 having the sound emitting hole 24, and faces the piezoelectric element 17 Provided is a piezoelectric acoustic conversion device, wherein an opening of a peripheral wall 32 of a case 25 is opened inside a housing 11.

Here, the piezoelectric element 17 has its piezoelectric film 19
Is preferably attached to the case 25 so as to face the side opposite to the sound output hole 24 of the housing 11. The piezoelectric element 17 may be attached to the step portion 13 provided on the inner circumference of the peripheral wall 32 of the case 25. Peripheral wall 32 of case 25
May have a lead wire fixing portion for fixing the lead wire 20 of the piezoelectric element 17. In addition, the peripheral wall 3 of the case 25
A part of the piezoelectric element 17 from the open end of the case 2 to the inside.
It is preferable to provide a protection member 29 that shields the outside of the unit 5.

[0008]

In the piezoelectric acoustic transducer according to the present invention, the case 2
The opening of the peripheral wall 32 of No. 5 is opened on the opposite side of the sound output hole 24 of the housing 11, that is, on the inside of the housing 11 .
Ri, because this is attached a piezoelectric element 17 in the peripheral wall 32, not a state where the piezoelectric element 17 is confined to the case 25 and the housing 11. Therefore, the piezoelectric element 17
It is easy to handle the lead wire 20. Also, case 2
It is possible to attach the piezoelectric element 17 to the case 25 after attaching the piezoelectric element 5 to the housing 11, and it is possible to easily replace the piezoelectric element 17 when the piezoelectric element 17 fails because only the piezoelectric element 17 needs to be replaced. In addition, the vibration source
Since the opening of the peripheral wall 32 of the case 25 facing the certain piezoelectric element 17 is attached toward the inside of the housing 11, the sound generated by the vibration of the piezoelectric element 17 is transmitted from the opening of the peripheral wall 32 of the case 25 to the housing. It is released inside 11. Therefore, the space inside the housing 11 can be used as an acoustic space, and the sound pressure can be easily ensured particularly in the low sound region.

Further, since the piezoelectric element is separated from the sound emitting hole 24 side of the housing 11 by the bottom wall 32 of the case 25, even if water enters from the sound emitting hole 24, it immediately comes into play. Don't touch 17. In particular, the piezoelectric film 19
When the piezoelectric element 17 is attached to the case 25 so that the piezoelectric element 17 faces away from the sound output hole 24 of the housing 11,
Even if water enters the inside, electrical troubles such as a short circuit of the piezoelectric element 17 are unlikely to occur.

When the piezoelectric element 17 is attached to the step portion 13 provided on the inner circumference of the peripheral wall 32 of the case 25, the piezoelectric element 17 can be stably attached to the case 25. In addition, the piezoelectric element 17 is attached to the peripheral wall 32 of the case 25.
When the lead wire fixing portion for fixing the lead wire 20 is provided, the lead wire 20 can be prevented from being broken by holding the lead wire 20. Further, when a protective member 29 for shielding a part of the piezoelectric element 17 from the outside of the case 25 is extended inward from the opening end portion of the peripheral wall 32 of the case 25, the case 25 incorporating the piezoelectric element 17 is provided in the housing 11. There is no fear that external force will be applied to the piezoelectric element 17 by a finger or the like when it is attached to the, and troubles such as damage can be prevented.

[0011]

Embodiments of the present invention will now be described in detail with reference to the drawings. FIG. 1 shows a housing 11 such as a so-called cordless phone handset. A recess is formed on the front surface of the earpiece, and a sound output port 24 is opened at the center of the deepest portion. On the inner surface of the housing 11, a case support portion 14 is provided upright in a cylindrical shape around the sound output hole 24.

The case 25 is made of resin,
An air braking hole 16 composed of a plurality of fine holes is bored in the center of the bottom wall 31, and a cylindrical peripheral wall 32 is provided upright from one surface of the bottom wall 31 around the air braking hole 16. This peripheral wall 32
A step portion 13 for mounting a piezoelectric element 17, which will be described later, is provided on the inner circumference of the. In addition, the peripheral wall 32 of the case 25
Groove 21 for passing the lead wire 20 of the piezoelectric element 17 at the edge of the
Is provided in the groove 21, and a lead wire fixing portion for fixing the lead wire 20 is provided in the groove 21 as described later. The bottom wall 3 is provided outside the peripheral wall 32 of the case 25.
A flange 30 is provided on the extension surface of 2.

The piezoelectric element 17 is formed by forming a piezoelectric film 19 on one surface or both surfaces of a diaphragm 18 made of a metal disk or the like, and further forming electrodes on the surface of the piezoelectric film 19.
The lead wires 20 are respectively formed on the electrode surfaces of the vibration plate 18 and the piezoelectric film 19.
Are connected, and the connector 23 is connected to the tip of the lead wire 20. In the illustrated embodiment, the so-called unimorph type piezoelectric element 17 in which the piezoelectric film 19 is provided only on one surface of the diaphragm 18 is used.

The piezoelectric element 17 is housed in a peripheral wall 32 with the piezoelectric film 19 side facing the side opposite to the bottom wall 31 side of the case 25, and the peripheral portion of the diaphragm 19 is placed on the step portion 13 with a silicone adhesive. It is glued and fixed with the like. In this state,
The piezoelectric element 17 is attached to the opening of the peripheral wall 32 of the case 25.
Is facing. The lead wire 20 of the piezoelectric element 17 is
It is drawn out of the case 25 through the groove 21 of the peripheral wall 32 and is fixed to the lead wire fixing portion in the groove 21. The piezoelectric element 17 can be attached in the direction opposite to the illustrated direction, that is, with the piezoelectric film 19 side facing the bottom wall 31 side of the case 25.
In order to avoid electrical troubles of No. 7, it is preferable to install in the direction shown.

In the case 25 in which the piezoelectric element 17 is incorporated in this way, the peripheral wall 32 on which the piezoelectric element 17 is attached is directed to the side opposite to the sound output hole 24 of the housing 11, that is, the inside of the housing 11, and the flange 30 is provided. Housing 1
It is placed on the case support 14 of No. 1 and is further fixed by the screw 22. At this time, the cushion material 12 such as a rubber ring is inserted between the bottom wall 31 of the case 25 and the housing 11. As a result, the case 25 is attached to the housing 11 such that the bottom wall 31 of the case 25 is spaced from the housing 11 and the air braking holes 16 and the sound output holes 24 face each other. Attach the case 25 in this way
By opening, the opening of the peripheral wall 32 of the case 25 becomes
The inside of the ging 11 is opened.

Further, the lead wire 20 drawn out of the case 25 through the groove 21 provided in the peripheral wall 32 of the case 25 has the housing 11 through the connector 23.
Is connected to an electronic circuit (not shown) provided inside. This completes the assembling of the piezoelectric element 17 into the housing 11.

FIG. 3 shows an example of the lead wire fixing portion provided in the groove 21 of the peripheral wall 32 of the case 25, and the lead wire 20 is fixed at this portion. That is, as shown in FIG. 3, a recess 33 and a protrusion 34 are provided in the groove 21 so as to face each other, and the lead wire 20 is passed between the recess 33 and the protrusion 34. The protrusion 34 has a steep rise inside the peripheral wall 32 and a gentle slope outside. Therefore, the lead wire 20 is bent in a U-shape between the recess 33 and the protrusion 34 and is passed through.
The resistance when pulling out the outside of the peripheral wall 32 is large. Therefore, the lead wire 20 is fixed so as not to be pulled out from the case 25, and disconnection due to excessive tension of the lead wire 20 is prevented.

FIG. 4 shows another example of the lead wire fixing portion.
In the example of FIG. 4A, protrusions 35 and 35 are provided to face each other in the groove 21 provided in the peripheral wall 32 of the case 25 so as to be displaced in the radial direction of the peripheral wall 32, and the lead wire 20 is
The protrusions 35, 35 are sewn together so as to pass through. Therefore, the resistance when pulling out the lead wire 20 to the outside of the peripheral wall 32 is large. On the other hand, in the example of FIG. 4A, the pin 3 is inserted in the groove 21 provided in the peripheral wall 32 of the case 25.
6, 36 are provided so as to face each other, and the lead wire 20 is passed while being sandwiched between the pins 36, 36. Therefore, the resistance when pulling out the lead wire 20 to the outside of the peripheral wall 32 is large. The recess 33, the protrusions 34 and 35, and the pins 36 and 36 face each other in the groove 21 in the circumferential direction of the peripheral wall 32 of the case 25.
Of course, they may be made to face each other in the vertical direction. Further, instead of the groove 21, a through hole may be used.

Next, the embodiment shown in FIG. 2 will be described. In this embodiment, the case 25 is not fixed to the housing 11 with screws, and the case 25 having no flange is attached to the case mounting portion 14 of the housing 11. As well as
Double-sided adhesive tape 26 that doubles as a cushion material and a spacer
The case 25 is adhered to the inside of the housing 11.
As a result, the case 25 is attached to the housing 11 in a state where the bottom wall 31 of the case 25 maintains an appropriate distance from the inner wall surface of the housing 11. The double-sided adhesive tape 26 is preferably made of an elastic material such as rubber or urethane foam. Further, in this embodiment, the sound emitting hole 24 of the housing 11 is provided with a damper 15 made of Tetron mesh or the like having a size of about # 380. On the other hand, the air braking hole 16 on the case 25 side is a single hole provided in the center of the bottom wall of the case 25.

[0020]

[0021]

[0022]

[0023]

[0024]

As described above, according to the present invention, the lead wire 20 of the piezoelectric element 17 can be easily handled, and the piezoelectric element 17 can be attached after the case 25 is attached to the housing 11. At the same time, the piezoelectric element 17 can be easily replaced when it fails. Furthermore, even if water enters from the sound output hole 24 of the housing 11,
Immediately it does not touch the piezoelectric element 17. As a result, it is possible to obtain a piezoelectric acoustic conversion device which is easy to assemble and replace the piezoelectric element and is less likely to be damaged by water. In particular, the piezoelectric film 19
When the piezoelectric element 17 is attached to the case 25 so that the piezoelectric element 17 faces the side opposite to the sound emission hole 24 of the housing 11, the electrical trouble of the piezoelectric element 17 due to water can be almost completely prevented.

If the piezoelectric element 17 is attached to the step portion 13 provided on the inner circumference of the peripheral wall 32 of the case 25, the piezoelectric element 17 can be stably attached to the case 25. The piezoelectric element 17 is attached to the peripheral wall 32 of the case 25.
If the lead wire fixing portion for fixing the lead wire 20 is provided, disconnection of the lead wire 20 can be prevented. Furthermore, the protective member 2 that shields a part of the piezoelectric element 17 from the outside of the case 25 inward from the opening end of the peripheral wall 32 of the case 25.
In the case where 9 is provided, troubles such as breakage of the piezoelectric element 17 can be prevented. Further, the opening of the peripheral wall 32 of the case 25
Has an opening toward the inside of the housing 11,
The space inside Jing 11 can be used as an acoustic space.
This makes it easier to raise the sound pressure, especially in the bass range,
You can get the pitch.

[Brief description of drawings]

FIG. 1 is a vertical sectional side view of a main part of a housing showing an embodiment of the present invention.

FIG. 2 is a vertical sectional side view of a main part of a housing showing another embodiment of the present invention.

FIG. 3 is a cross-sectional plan view of essential parts showing an example of a lead wire fixing portion of a case in the embodiment.

FIG. 4 is a cross-sectional plan view of essential parts showing another example of the lead wire fixing portion of the case in the embodiment.

FIG. 5 is a vertical sectional side view of a main part of a housing showing a conventional example.

Continued front page    (72) Inventor Fumihisa Ito               6-16-20 Ueno, Taito-ku, Tokyo Sun               Inside the dielectric                (56) Bibliography Actual Kaihei 4-12739 (JP, U)                 Actual Development Sho 54-110080 (JP, U)

Claims (4)

(57) [Claims] 1. A piezoelectric acoustic conversion device comprising a piezoelectric element (17) attached to a case (25) and the case (25) attached inside a housing (11) having a sound output hole (24). 25) is an air braking hole (1
The vibrating plate (18) has a bottom wall (31) having 6) and a peripheral wall (32) standing up from the peripheral portion of the bottom wall (31 ).
The peripheral portion of the piezoelectric element (17) having the piezoelectric film (19) formed on one side or both sides of the peripheral wall (3) of the case (25).
The case (25) is attached to the inner circumference of 2), and the case (25) is attached to the inside of the housing (11) having the sound output hole (24) and faces the piezoelectric element (17).
A piezoelectric acoustic conversion device, characterized in that the opening of the peripheral wall (32) of the case (25) opens inside the housing (11). 2. The piezoelectric element (1) according to claim 1,
7) is a piezoelectric acoustic conversion device in which the piezoelectric film (19) is attached to the case 25 so that the piezoelectric film (19) faces the sound emission hole 24 of the housing (11). 3. The piezoelectric element according to claim 1 or 2, wherein the piezoelectric element (17) is attached to a step portion (13) provided on the inner circumference of the peripheral wall (32) of the case 25. Acoustic transducer. 4. The lead wire fixing portion according to claim 1, further comprising a lead wire fixing portion for fixing the lead wire (20) of the piezoelectric element (17) to the peripheral wall (32) of the case (25). Piezoelectric transducer.