JPS5852398B2 - Electroacoustic transducer using a tuning fork type piezoelectric vibrator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electroacoustic transducer using a tuning fork type piezoelectric vibrator, such as a microphone, an earphone, or a speaker.

For example, conventional general basic structures of microphones include the carbon type, which uses electrical resistance, and the magnetic type, which uses electromotive force from the movement of a diaphragm within a coil. There are also the dynamic type, which uses electromotive force from the vibration of a coil within the lines of magnetic force, and the crystal type, which uses the piezoelectric effect of Rochelle salt, and more recently, the capacitor type. There are some methods that use changes in electric capacitance.

However, at present, a device using the crystal piece according to the present invention has not yet been put into practical use.

The reason for this is that the crystal material itself has conventionally relied on natural crystal, which is expensive enough to be classified as jewelry, and the portion that can be used electrically is limited.In addition, the material cost is high due to the above-mentioned In addition, using a crystal piece in the audio frequency range required a relatively large area, making it difficult to create a compact microphone. That's true.

However, recently, the manufacturing technology of artificial quartz has progressed dramatically,
At the same time, with the expansion of piezoelectric elements for electronic watches, extremely miniaturized crystal oscillators have been realized.

An object of the present invention is to provide an ultra-small electroacoustic transducer with high sensitivity and stable characteristics by utilizing tuning fork type piezoelectric vibrators that have recently been mass-produced for electronic watches.

Embodiments of the present invention will be described below regarding an ultra-small microphone using a tuning fork type crystal resonator.

FIG. 1 shows a partial sectional view of the front view of the embodiment of the present invention, and FIG. 2 shows a partial sectional view of the side view of the embodiment of FIG.

One vibrating piece 2 of the tuning fork type crystal oscillator 1 is attached to a circular substrate 4 via a fixed base 3 made of an insulator, and the handle 5 corresponding to the vibration nodes and the other vibrating piece 6 are lifted from the substrate 4. Lead wires 7 and 8 are led out from a pair of electrodes on the crystal resonator 1.

A cylindrical member 9 is glued around a circular substrate 40 to form a box shape with one side open, and a vibrating body 10 made of polyester or the like is stretched over the open side to seal the inside of the box. The central portion corresponding to the antinode of vibration and the tip of the other vibrating piece 6 of the crystal resonator are connected by a needle-like connecting member 11.

Further, a conductive material such as aluminum is deposited on one or both surfaces of the vibrating body, and conductive layers are also provided on the inner or outer peripheral surfaces of the circular substrate 4 and the cylindrical member 9 to electrostatically shield the crystal resonator.

At this time, the lead wire 7 of the electrode that is electrically connected to the conductive layer of the vibrating body is used as the ground terminal, and the lead wire 8 of the electrode that is electrically insulated from the electrostatic shield body by the fixed base 3 is used as the ground terminal. Used as a signal output terminal.

When a crystal resonator for an electronic watch with a total length of 6 mm was used as an example of the present invention, an ultra-small microphone with an outer diameter of 127 mm and a thickness of 3 mm was obtained.

FIG. 3 shows a partially sectional front view of a microphone that is a further improvement of the above embodiment, and FIG. 4 shows its circuit diagram.

The differences between this embodiment and the previous embodiment will be explained below, and the same parts will be designated by the same numbers.

A circular board 14 is made of a printed wiring board, and an FET (field drop transistor) 1 is installed to amplify the electromotive force of the crystal resonator.
5 is mounted in a box shape on a substrate 14, the electrodes of the crystal resonator 1 and the FET 15 are wired in the box shape, and the output signal of the FET 15 is led out to the outside by a lead wire.

Furthermore, the conductive foil of the printed wiring board 14 is used as a part of the electrostatic shield.

The electrical signal from the electrode of the crystal oscillator is immediately input to the gate electrode of FET 15, but since the wiring between them is inside the electrostatic shield, it is completely unaffected by external electromagnetic fields, and the impedance is converted from high impedance to low impedance. Moreover, since the signal is amplified and then output to the outside through a lead wire, a microphone with an excellent signal-to-noise ratio can be obtained.

FIG. 5 is a front view of another embodiment of the present invention, and FIG. 6 is a side view thereof, both with the case cut away.

The vibrating abdomen 24 of one vibrating piece of the tuning fork crystal resonator 23 is directly soldered to the gate electrode terminal 22 of the FET 21 to support the crystal resonator, and the crystal resonator is attached to the bottom of the case 25 with one side of the rectangular opening. The vibrating body 26 is stretched over the opening surface of the case, and the center of the vibrating body 26 and the vibrator 23
The other vibrating abdomen 27 is connected by a needle-like connecting member 28.

Then, in the same manner as in the above embodiment, a conductive layer is provided on the circumferential surface of the case to form an electrostatic shield, and the drain electrode terminal 29 of the FET 21 is connected to this shield, and the FET 2
1 source electrode terminal 30 and lead wire 3 from the shield body
Derive 1.

A microphone with such a structure has a diameter of 5m7I, for example.
By housing the microphone in the tip 32 of a thin pipe-like case of about L size and making a small hole 33 at a location facing the diaphragm 26, an ultra-small microphone with a new external shape can be obtained.

The front sensitivity frequency characteristic of the microphone in the above example is 40
It exhibited uniform characteristics over a high range of Hz to 40,000 Hz (-10 dB), and not only fell under JIS classification AI, but also exhibited extremely excellent characteristics in terms of voice clarity and fidelity.

Moreover, the directional characteristics were omnidirectional.

[Brief explanation of the drawing]

FIG. 1 is a partial sectional view of a front view of an embodiment of the present invention, and FIG.
The figure is a partial sectional view of a side view of the embodiment shown in FIG. 1, FIG. 3 is a partial sectional view of a front view of another embodiment of the present invention, and FIG.
FIG. 5 is a partial sectional view of a front view of still another embodiment of the present invention, and FIG. 6 is a partial sectional view of a side view of the embodiment shown in FIG. 1.23...Crystal resonator, 4,9,25...
... Fixed member, 10, 26 ... Vibrating body, 11
, 28... Connection member, 15... FET
.

Claims (1)

[Scope of Claims] 1. One vibrating piece of a tuning fork type piezoelectric vibrator is attached to the bottom surface of the box-shaped fixing member to support the vibrator, and the vibrating body is stretched over the opening surface of the box-shaped fixing member. An electroacoustic transducer using a tuning fork type piezoelectric vibrator, characterized in that the central part of the vibrating body and the tip of the other vibrating piece of the tuning fork type piezoelectric vibrator are connected by a connecting member. 2. An electroacoustic transducer using a tuning fork type piezoelectric vibrator according to claim 1, characterized in that an impedance conversion element is built into the box-shaped fixing member. 3. A conductive layer is provided on the inner peripheral surface or outer peripheral surface of the box-shaped fixing member and the vibrating body to provide electrostatic shielding. An electroacoustic transducer using a tuning fork type piezoelectric vibrator. 4. An electroacoustic transducer using a tuning fork type piezoelectric vibrator according to claim 1, wherein the tuning fork type piezoelectric vibrator is a tuning fork type piezoelectric vibrator for an electronic watch. 5. An electroacoustic transducer using a tuning fork type piezoelectric vibrator according to any one of claims 1 to 4, wherein the tuning fork type piezoelectric vibrator is a tuning fork type crystal vibrator.