JPS6022717Y2 - Piezoelectric electroacoustic transducer - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a piezoelectric electroacoustic transducer incorporated into a telephone or the like.

Conventionally, as shown in FIG. 1, this type of piezoelectric electroacoustic transducer has been constructed by pasting a piezoelectric ceramic thin plate 1 onto a metal diaphragm 2 with an adhesive or the like, and surrounding the metal diaphragm 2 with a housing 3. It is known that it is supported and fixed.

Generally, the piezoelectric ceramic thin plate 1 has a diameter of 10 to 307 cm.
A thin disk with a diameter of 71711φ and a thickness of 0.1 to 0.4rlrIn is used, and the metal diaphragm 2 has a diameter of 15 to 4o7rr.
Inφ, thickness 0. A thin disk of ~0.4 mm is used.

The resonance frequency is often about 2 to 1 kHz.

To take out the electrodes from the piezoelectric ceramic thin plate 1, the piezoelectric ceramic thin plate 1 is bonded to the metal diaphragm 2 using an adhesive.
This is accomplished by soldering one of the two twisted conductive wires 4 and 5 of about 1 diagonal diameter to the surface electrode of the piezoelectric ceramic thin plate 1 and the other to the metal diaphragm 2.

However, the electrode extraction method using such twisted conductive wires 4 and 5 has various problems as described below.

First of all, the visibility of the stranded conductors 4 and 5 is impaired at the soldered parts, and especially when they are installed in locations with large vibrations, there are many cases where the soldered parts break due to fatigue due to stress concentration. .

In addition, since the stranded conductor wire 4.5 is routed through a limited space inside the small housing 3, coated wire is used to prevent short circuits, but in this case, the amount of stiffness increases and the resonance frequency of the metal diaphragm 2 is reduced. This causes variation.

Furthermore, when soldering the twisted conductor wires 4 and 5 to the metal diaphragm 2, it is difficult to adjust the solder strength and solder amount because the wires are brought into contact with the surfaces, and variations in the solder amount are the cause of variations in the resonant frequency. becomes.

In addition, when using stranded conductor wires, the amount of solder applied to the metal diaphragm and piezoelectric ceramic thin plate requires a certain amount of solder in the locations, otherwise it takes time and effort to store it inside the housing or pull it out of the housing. The drawback is that it requires space and is difficult to downsize as a whole.

This invention was made in view of the above points, and aims to provide a piezoelectric electroacoustic transducer that is small, highly reliable, and has a simple assembly structure by improving the electrode extraction structure.

In this invention, the casing is constituted by a metal outer cylinder having a bottom plate and a metal inner cylinder housed within the outer cylinder with an insulator interposed on the inner wall except for the top of the bottom plate.

Then, using an electrode extraction member made of a flexible printed board having a tongue piece, this is held between the bottom plate of the external cylinder and the bottom of the internal cylinder together with the metal diaphragm, and one electrode of the piezoelectric ceramic thin plate is used. The other electrode is electrically connected to the outer cylinder and the inner cylinder through the metal diaphragm and the electrode extraction member, respectively.

Here, the electrode extraction member has a ring or arc shape with approximately the same diameter as the metal diaphragm, and the plastic film on the back surface in contact with the metal diaphragm is removed at least at the tip, so that the electrode extraction member has tongue pieces that protrude inward. is provided, and the tip of this tongue piece is fixed to the electrode of the piezoelectric ceramic thin plate.

The metal diaphragm, the electrode extraction member, and the internal cylinder are housed in this order in the external cylinder to integrate them.

Examples of this invention will be described below.

FIG. 2 is a sectional view of a main part of one embodiment, and FIG. 3 is an exploded perspective view.

In the figure, reference numeral 11 denotes a metal outer cylinder which is a first ring body, and a metal inner cylinder 12 which is a second ring body is accommodated in this to form a housing.

An insulator 13 is interposed between the outer cylinder 11 and the inner cylinder 12 for electrical insulation.

Reference numeral 14 designates a metal diaphragm, on the surface of which a piezoelectric ceramic thin plate 15 is adhered in advance with an adhesive or the like, and this is sandwiched between the bottom plate of the external cylinder 11 and the bottom surface of the internal cylinder 12 at its periphery. has been done.

An electrode extraction member 16 is sandwiched between the internal cylinder 12 and the metal diaphragm 14.

The electrode extraction member 16 is formed into an annular shape with an outer diameter approximately equal to that of the inner cylindrical body 12, using a flexible printed board with a thickness of about 1100 IL, which is made by laminating a plastic film 161 and a metal foil 16□ such as copper. At the end, there is a tongue piece 1 that protrudes inward from which the plastic film on the back side is removed at the tip.
63 are provided.

The tip of this tongue piece 163 is the piezoelectric ceramic thin plate 1.
It is soldered to the surface electrode of 5.

For assembly, for example, the tip of the tongue piece 163 of the electrode extraction member 16 is pre-soldered, and the insulator 13 is attached to the external cylinder 11.
, a metal diaphragm 14 to which a piezoelectric ceramic thin plate 15 is attached.
, drop the electrode extraction member 16 in this order, solder the tongue piece 163 of the electrode extraction member 16 to the surface electrode of the piezoelectric ceramic thin plate 15, insert the inner cylindrical body 12, and attach it to the outer cylindrical body 11 by caulking or using a mounting agent. This can be easily done by fixing the inner cylindrical body 12.

Thus, in this embodiment, one electrode of the piezoelectric ceramic thin plate 15 is led to the outer cylinder 11 via the metal diaphragm 14, and the other electrode is led to the inner cylinder 11 through the electrode extraction member 16 made of a flexible printed board. guided by.

According to this embodiment, unlike the conventional electrode extraction structure using twisted conductor wires, the electrode extraction member made of a flexible printed board is integrally housed in the housing together with the metal diaphragm, and the tongue piece of the electrode extraction member is also placed at the tip. The metal foil is exposed only at the beginning, and the rest is lined with a flexible, resilient plastic film, which eliminates stress concentration and enables stable and reliable electrode extraction.

Further, the electrode extraction member has a small stiffness and does not adversely affect the resonance frequency of the metal diaphragm.

Furthermore, since electrical connection is made over the shortest distance between the casing, which forms part of the electrical terminal, and the piezoelectric ceramic thin plate, the internal volume of the casing can be reduced, and the device can be made more compact.

Since the metal diaphragm is held between the inner cylinder and the outer cylinder together with the flexible printed board, the metal diaphragm is firmly fixed and there is no loosening that would impede the vibration of the metal diaphragm.

Furthermore, if you pre-solder the tip of the tongue piece, there is no need to adjust the amount of solder or position the solder on the metal diaphragm, and the assembly process is just stacking each part one by one and integrating them. It is extremely simple.

Furthermore, the fact that the outer cylinder and the inner cylinder that form the housing are conductive, and that they form part of the electrode lead of the piezoelectric ceramic thin plate as they are, is an example of a structure in which the electrode lead is provided by penetrating the cylinder. It is easier to assemble compared to

Furthermore, since the casing is conductive, it has an electrical shielding effect.

In addition, both the external cylinder and the internal cylinder that make up the housing are made of metal, which has superior workability compared to, for example, resin.
The outer periphery of the metal diaphragm can be fixed with excellent parallelism.

This stabilizes the resonance frequency.

Furthermore, the outer cylinder and the inner cylinder are electrically separated by an insulator, and the outer diameters of the metal diaphragm, electrode extraction member, and inner cylinder are the same, and they are housed inside the outer cylinder without play. can do.

In particular, it is important to fix the outer periphery of the metal diaphragm so that there is no deviation in the position of the clamp, which is important for stabilizing the sensitivity and resonance frequency. This will improve physical characteristics and reliability.

In the above embodiment, the electrode extraction member was constructed in an annular shape using a flexible printed board, but as shown in Fig. 4, only the necessary arc-shaped part was constructed with the flexible printed board, and the other parts were A plastic plate 21 having the same thickness as this flexible printed board may be interposed as a spacer.

Considering the thickness of the flexible printed board inside the housing, the fourth
The plastic plate 21 serving as a spacer may be extremely thin as long as a recess is provided in the portion where the arcuate electrode extraction member 16 shown in the figure is placed.

In the above embodiment, the plastic film is removed only from the tip of the tongue piece of the electrode extraction member, but if the metal foil has the necessary flexibility, the plastic film can be removed from the entire tongue piece. It is also possible to remove it and leave only the metal foil.

This invention is also useful when the metal diaphragm, piezoelectric ceramic thin plate, and housing are rectangular.

As described above, according to this invention, the outer periphery of the metal diaphragm is stably fixed by the coaxial metal outer cylinder and inner cylinder, and the electrode extraction member made of a flexible printed board is used to ensure reliability. It is possible to provide a piezoelectric electroacoustic transducer that has high performance, is easy to downsize, has a simple assembly structure, and has extremely stable electrical characteristics.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of the main parts of a conventional piezoelectric electroacoustic transducer, Fig. 2 is a sectional view of the main parts of a piezoelectric electroacoustic transducer according to an embodiment of the invention, and Fig. 3 is an exploded perspective view. FIG. 4 is a diagram showing a modified example of the electrode extraction member. 11... External cylindrical body (first ring body), 12.
...Inner cylindrical body (second ring body), 13...
...Insulating material, 14...Metal diaphragm 15...
...Piezoelectric ceramic thin plate, 16, 16A, 16B...
...Electrode extraction member, 161...Plastic film, 16□...Metal foil, 163...
- Tongue piece, 31, 41...First ring body, 32
,42...2nd dialogue, 43,44.44
A, 44B...Terminal board.

Claims (1)

[Scope of utility model registration request] A housing is constituted by a metal external cylinder having a bottom plate, and a metal internal cylinder housed inside the external cylinder with an insulator interposed on the inner wall except for the top of the bottom plate, and the bottom plate of the external cylinder An electrode extraction member consisting of a metal diaphragm to which a piezoelectric ceramic thin plate is attached and a flexible printed circuit board in the shape of a ring or an arc having approximately the same diameter as the metal diaphragm is held between the bottom of the inner cylinder and the electrode extraction member. The member has a tongue piece that protrudes inward by removing at least the tip of the plastic film on the back surface in contact with the metal diaphragm, and the tip of the tongue piece is fixed to the electrode of the piezoelectric ceramic thin plate, Further, one electrode of the piezoelectric ceramic thin plate is electrically connected to the outer cylindrical body and the inner cylindrical body via the metal diaphragm, and the other electrode is electrically connected to the outer cylindrical body and the inner cylindrical body, respectively, via the electrode extraction member. A piezoelectric electroacoustic transducer.