JPS5852399B2 - 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, earphone, or speaker.

Recently, the manufacturing technology of artificial quartz has progressed dramatically, and at the same time,
With the establishment of mass production technology for ultra-compact crystal units for electronic watches, ultra-compact units with excellent performance can now be provided at low prices.

In view of the above, the present invention separately proposes an electroacoustic transducer using a tuning fork type piezoelectric vibrator that can be used to manufacture an ultra-small microphone earphone.

A crystal microphone, which is an example of such a microphone, exhibits even better performance characteristics than a condenser microphone, is small in size and inexpensive, and is therefore expected to develop in the future.

The present invention provides a technology that can arbitrarily control the characteristics of this crystal microphone, particularly the sensitivity frequency characteristics, and extends the use of the crystal microphone from the audio frequency band to the ultrasonic band.

Embodiments of the present invention implemented in microphones will be described below with reference to the drawings.

FIG. 1 is a front view of an embodiment of the present invention, FIG. 2 is a partial sectional view of the front view, and FIG. 3 is a partial sectional view of the side view of the embodiment.

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 attached around the circular substrate 4 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 the vibration of the crystal resonator 10 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.

Such a device can be used as a complete electroacoustic transducer.

That is, when the vibrating body 10 vibrates due to sound waves, it can be extracted as an electrical signal from the lead wires 7 and 8, and conversely,
When an audio electric signal is applied between the lead wires 7.8, the vibrating body 10 vibrates and becomes a sounding body.

A characteristic part of the present invention is that a flexible adjusting body, for example, a rubber plate 12, is attached to the outer circumference of the vibrating body 10 with an adhesive in order to arbitrarily control the sensitivity frequency characteristics of the electroacoustic transducer. It is in the combined point.

By bonding such adjustment bodies 12 together, the upper limit of the frequency band is expanded to the high frequency side.

According to experiments, the dimensions of the crystal oscillator were 6 mm in total length x 1 mm in width.
A prototype microphone with dimensions of 6 mm x 0.5 mm in thickness and a vibrating body of 12 mm in diameter x 3.8 mm in thickness was manufactured, and its sensitivity frequency characteristics were measured, and the characteristics shown in FIG. 4 were obtained.

Next, a rubber plate with an outer diameter of 12 mm x inner diameter of 61 mm x 0.5 mm was pasted on the vibrating body of the microphone with adhesive, and the sensitivity frequency characteristics were measured again.
The characteristics shown in the figure were obtained.

The adjusting body 12 of the present invention can be implemented by pasting a plate-like material of rubber or soft plastic, or by coating or printing plastic or a material containing plastic.

FIG. 6 shows a front view of another embodiment of the invention.

The feature of this embodiment is that a ring-shaped adjusting body 12 is attached to the outer circumference of the vibrating body 10, and a circular adjusting body 13 is also attached to the center of the vibrating body 10.

The adjusting body 13 in the center is made of flexible materials such as rubber, etc.
Metals such as lead and copper can be used, and the shape is not necessarily limited to a circle.

As a result, the mass of the vibrating body is substantially increased, and the sensitivity in the low frequency band can be improved despite being ultra-compact.

Therefore, by appropriately selecting the material and shape of the adjusting body 10 at the outer circumference and the adjusting body 12 at the center, characteristics suitable for the purpose of use can be easily obtained.

Further, the shape of the vibrating body of the present invention is not limited to the circular shape of the above embodiments, but may be rectangular, elliptical, etc., and the shape of the adjusting body to be bonded can also be modified accordingly. can.

According to the present invention, one end of the tuning fork type piezoelectric vibrator is fixed and the other end is connected to the center of the vibrating body, so the resonant frequency of the entire device is much lower than the resonant frequency of the tuning fork type vibrator itself. Therefore, even if the resonant frequency of the vibrator itself is higher than the audible frequency, it is possible to obtain excellent characteristics in the audible frequency region as a whole.

This has made it possible to manufacture microphones or earphones for audio frequency bands in an ultra-compact size and at low cost by directly using tuning fork-type piezoelectric vibrators for electronic watches, which have become rapidly popular in recent years.

Further, according to the present invention, by selecting the shape and dimensions of the flexible material bonded only to the outer periphery of the vibrating body, the frequency characteristics, particularly the sensitivity characteristics in the high frequency range of audio frequencies, can be arbitrarily controlled.

Therefore, while mass-producing microphones and the like having the same basic shape and dimensions, it is possible to easily manufacture a wide variety of products with somewhat different frequency characteristics depending on the purpose of use.

[Brief explanation of drawings]

FIG. 1 is a front view of an embodiment of the present invention, FIG. 2 is a partial sectional view thereof, and FIG. 3 is a partial sectional view of a side view of the above embodiment. FIGS. 4 and 5 are diagrams showing the sensitivity frequency characteristics of the present invention without the adjustment body and with it. FIG. 6 is a front view of another embodiment of the invention. 1...Crystal resonator, 4...Fixing member,
10... Vibrating body, 11... Connecting member,
12...Adjustment body.

Claims (1)

[Claims] 1 One vibrating piece of a tuning fork type piezoelectric vibrator is attached to the bottom of the box-shaped fixing member to support the vibrator, a vibrating body is stretched over the opening of the box-shaped fixing member, and the center of the vibrating body is attached to the bottom of the box-shaped fixing member. In a device in which the tip of the tuning fork type piezoelectric vibrator and the tip of the other vibrating piece of the tuning fork type piezoelectric vibrator are connected by a connecting member, an adjustment body made of a flexible material such as rubber is bonded only to the outer periphery of the vibrating body. An electroacoustic transducer using a tuning fork type piezoelectric vibrator, which is characterized by: