JPS5852400B2 - 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 ultra-small microphones and earphones.

A crystal microphone, which is an example of such a microphone, exhibits various characteristics superior to a condenser microphone, and is also small and inexpensive, and is therefore expected to develop in the future.

The present invention provides a technique that allows the characteristics of this crystal microphone, particularly the sensitivity frequency characteristics, to be controlled at any time.

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 thereof, and FIG. 3 is a partial sectional view of a side view of the above 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 bonded 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. A needle-shaped connecting member 11 connects the central portion corresponding to the antinode of vibration with the tip of the other vibrating piece 6 of the crystal resonator.

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 feature of the present invention is that an adjustment body 12 is attached to the center of the vibrating body 10 in order to arbitrarily control the sensitivity frequency characteristics of the electroacoustic transducer described above.

When a flexible material such as rubber or soft plastic is used as the adjusting body 12, the upper limit of the frequency band of the frequency characteristic curve shifts to the lower frequency side, and the peak of sensitivity is obtained in the upper limit band.

Furthermore, when a high-density metal such as lead or copper is used as the adjustment body 12, a very sharp sensitivity peak is obtained at a specific frequency determined depending on the mass of the adjustment body 12.

According to experiments, the dimensions of the crystal oscillator are 6 mm in total length x 1.6 mm in width.
A prototype microphone with a diameter of 12 mm and a thickness of 3.8 mm and a vibrating body of 12 mm in diameter and 3.8 mm in thickness was measured, and the characteristics shown in FIG. 4 were obtained.

Next, place a diameter of 7 mm in the center of the vibrating body of the microphone.
When a rubber plate having a thickness of 0.5 mtrt was attached with an adhesive and the sensitivity frequency characteristics were measured again, the characteristics shown in FIG. 5 were obtained.

In addition, as another experiment, using a microphone with the characteristics shown in Figure 4 above, we attached a piece of lead of a predetermined mass to the center of the vibrating body and measured the sensitivity frequency characteristics, as shown in Figure 6. Characteristics with very sharp dynamics were obtained.

As the value of this mass is gradually increased, the peak frequency gradually shifts to the lower frequency side, as shown from ■ to [phase] in Figure 6, and the peak frequency is controlled by the mass value. became clear.

To explain this in more detail, when a circular lead plate with a thickness of 0.2 mm and a diameter of 3 squares is attached, the characteristics shown by ■ in Fig. 6 are obtained, and a circular lead plate with a thickness of 5.0 mm and a diameter of 10 squares is obtained. When a lead plate was attached, the characteristics shown by [phase] in FIG. 6 were obtained.

Further, the shape of the vibrating body of the present invention is not limited to the circular shape of the above embodiment, but can be implemented as a rectangle, an ellipse, etc., and the shape of the acoustic shielding plate to be bonded can be modified accordingly. Can be done.

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.

Furthermore, according to the present invention, when attaching a flexible material such as a rubber plate to the center of the vibrating body, the upper limit of the frequency band moves to the lower frequency side, and when attaching a high-density metal, the selectivity increases. A sharp frequency characteristic can be obtained, and the peak frequency can be controlled according to the mass of the adjustment body.

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 slightly different frequency characteristics depending on the purpose of use without reducing conversion efficiency.

Furthermore, by using a high-density metal as the adjustment body, a sharp frequency characteristic with selectivity that peaks at an arbitrary frequency can be obtained, making it possible to easily and inexpensively manufacture frequency analyzers, noise measuring devices, scale display devices, etc. Can be done.

[Brief explanation of the drawing]

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. FIG. 4 is a diagram showing sensitivity frequency characteristics of a device not provided with the adjusting body of the present invention, and FIGS. 5 and 6 are diagrams showing sensitivity frequency characteristics of a device provided with the adjusting body of the present 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. and the tip of the other vibrating piece of the tuning fork type piezoelectric vibrator are connected by a connecting member, characterized in that an adjustment body is attached to the center of the vibrating body. Electroacoustic transducer using a child.