JPS593674Y2 - Piezoelectric buzzer structure - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a piezoelectric buzzer structure, and particularly to the structure of a piezoelectric element attached to a diaphragm.

The main purpose of the present invention is to easily adjust the volume of a piezoelectric buzzer.

In recent years, many watches equipped with alarm devices have been released.
The number is increasing year by year.

As a result, alarm sounds, which were initially rare, can now cause discomfort to others depending on the location and time of day.

Therefore, many methods for freely adjusting the volume of the alarm sound have been studied.

The main methods include changing the tenacity ratio of the drive waveform and changing the applied voltage.

The method of adjusting the volume by changing the duty ratio is very convenient because the drive waveform can be easily created using the integrated circuit configuration.

However, as shown in FIG. 1, this method is not so preferred for piezoelectric buzzers.

In FIG. 1, the vertical axis is the sound pressure in dB, and the horizontal axis is the duty ratio.

In the figure, A is the sound pressure of the electromagnetic buzzer, and B is the sound pressure of the piezoelectric buzzer.

As is clear from the figure, the sound pressure of electromagnetic buzzers changes in proportion to the duty ratio, but the difference is not so clear for piezoelectric buzzers.

The drive signal to the piezoelectric buzzer is generally a high voltage signal boosted by a boost coil, and this high voltage signal is
This is because it occurs when the signal input to the boost coil is cut off, and does not depend much on the duty ratio.

As described above, it is not preferable to adjust the volume of the piezoelectric buzzer based on the duty ratio.

Next, there is a method of applying an applied voltage, but this method also applies to piezoelectric buzzers, as shown in Figure 2, the sound pressure dB (Fa axis) and the applied voltage (horizontal axis) change almost proportionally, and the volume can be adjusted. It's easy.

However, when changing the applied voltage, the battery voltage must be reduced, and one constant voltage circuit is required for one voltage, which requires at least a transistor and a resistor.

Therefore, when performing volume adjustment in multiple stages, a number of transistors and resistors corresponding to the number of stages are required, which greatly increases the number of circuit components, which is disadvantageous in terms of space and cost.

The present invention eliminates these drawbacks and provides a method that allows volume adjustment easily and reliably.

This will be explained below by giving examples. FIG. 3 shows an embodiment of the present invention, in which 1 is a metal or plastic diaphragm, and 2 is a piezoelectric element divided into four parts.

FIG. 4 shows a piezoelectric buzzer drive circuit of this embodiment, where 3 is a transistor, 4 is a booster coil, 5 is a switch, and 2 is the divided piezoelectric element shown in FIG.

As shown in FIG. 5, the volume of the piezoelectric buzzer increases in proportion to the area of the piezoelectric element, that is, the number of piezoelectric elements attached to the diaphragm.

In FIG. 5, the vertical axis is the sound volume dB, and the horizontal axis is the piezoelectric element area S.

Therefore, to obtain a normal loud alarm sound, all switches 5 in FIG. 4 may be closed.

Furthermore, if you want to reduce the volume, you can close part of the switch 5.

Furthermore, to change the volume in stages, it is sufficient to close the switches 5 in sequence.

Therefore, for example, although not described in detail, by providing a switch 5 that rotates with the passage of time, it is possible to easily create a device that increases the volume in proportion to the passage of time.

Further, the number of components such as transistors does not increase, and the layout design of the circuit board is easy.

As described above, according to the present invention, the volume of the piezoelectric buzzer can be easily and reliably adjusted, and has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing the relationship between the sound pressure and the duty ratio of a piezoelectric buzzer and an electromagnetic buzzer. Fig. 2 is an explanatory diagram showing the relationship between sound pressure and applied voltage of the piezoelectric buzzer, Fig. 3 is a perspective view showing an embodiment of the present invention, and Fig. 4 is an explanatory diagram of the piezoelectric buzzer drive circuit of the present embodiment. , Figure 5 is
FIG. 2 is an explanatory diagram showing the relationship between the area of a piezoelectric element and sound pressure. 1... Vibration plate, 2... Piezoelectric element, 3.
...Transistor 4...Boost coil, 5...Switch.

Claims (1)

[Scope of utility model registration request] In a piezoelectric buzzer formed by at least a piezoelectric element and a diaphragm, at least two or more piezoelectric elements are attached to the diaphragm in parallel, and the juxtaposed piezoelectric elements are connected to a drive circuit through independent circuits, and , each of the connections has a switch means, and the other end of the switch is wired together and connected to a power source via a transistor, and the plurality of switch means are selectively closed circuits to adjust the volume. A piezoelectric buzzer structure characterized in that it is configured to adjust.