JPS60223300A - Piezoelectric buzzer - Google Patents

Abstract

PURPOSE:To improve the sound quality by bonding a piezoelectric member containing different electrodes to a common diaphragm and driving these different eletrodes with different frequencies. CONSTITUTION:A common diaphragm 1 is used as an electrode at one side, and two electrodes 3 are formed on a piezoelectric member 2 bonded to the diaphragm 1. This diaphragm 1 of a piezoelectric buzzer 16 is set at a VDD level, and both electrodes 3 are driven by the signals given from a single frequency generating system respectively. Two acoustic signals having different frequencies are mixed audibly by the diaphragm 1. In such a way, the sound quality is improved.

Description

[Detailed description of the invention] 〔Technical field〕 The present invention relates to an electrode shape of a piezoelectric buzzer.

[Prior art]

The structure of a conventional piezoelectric buzzer is as shown in FIG. 6, in which a diaphragm 1 made of a single metal thin plate is used as the first electrode, a piezoelectric member 2 is attached to the imaging plate, and a vapor deposition process is performed on the piezoelectric member. A thin metal film 3 is formed by using this method, and this serves as the second electrode.The piezoelectric buzzer is used to generate a plurality of sounds depending on the period of change in the voltage applied between the two electrodes. When trying to perform electroacoustic conversion of signals with different beat frequencies (
has the following drawbacks:

Generally, the sound pressure of a piezoelectric buzzer is affected by the amount of charge, so a circuit configuration as shown in FIG. 4 is used as the drive circuit.

In the same figure, (al) is a basic circuit, and (t)l is a method for increasing the drive current to reduce the voltage. In the circuit in the same figure, the acoustic signal generated from the piezoelectric buzzer is attenuated. The first method is to connect multiple transistors in parallel, each with a different current supply ability, as shown in Figure 5 (at).

The second method is to connect to the base end of a bipolar transistor and switch back each current supply transistor to gradually reduce the pace current and obtain sound pressure attenuation.The second method is to gradually change the duty as shown in Fig. 2(b). A well-known method is to apply a waveform to the base end of the bipolar transistor to reduce the time of the bipolar transistor, thereby gradually decreasing the average current flowing through the collector, thereby obtaining sound pressure attenuation.

On the other hand, when multiple frequencies are combined to drive a piezoelectric buzzer or other similar transducer, in the prior art, the outputs of frequency generating systems 4 and 5 of The signals are electrically mixed, and the mixed waveform drives the electrical sound # converter. Figure (b) shows the generation of rectangular waves with different frequencies θ from the single frequency generation system 4°5. is output and represents the state of electrically mixed molding.

However, in a typical piece of music in which the main melody and accompaniment are composed of two or more overtones, the timing of the occurrence of the main melody and accompaniment notes is completely asynchronous, meaning that the decay of each note of the main melody and accompaniment must be performed asynchronously. Therefore, in the conventional current supply transistor switching method, since the waveform after mixing is used for driving, both heavy sounds receive the same attenuation, and the method for controlling the duty of the waveform is as shown in FIG. 6(b).
Since the above mixing waveform cannot control the 08 time of the pibo 2 transistor as described above, it cannot be applied.

Therefore, conventional piezoelectric buzzers employ a method that uses the discharge characteristics of a capacitor to attenuate the acoustic signal. A specific example using this method is shown in FIG. In the figure, a short pulse is generated asynchronously from each single melody generation system 6.7 to the first switch 8.
.
FF. On the other hand, each of the single melody generation systems outputs a signal having a frequency corresponding to the pitch of each note, and is applied to the second switch 12.13 degrees. The second
The switch alternately connects and disconnects the voltage between one end of the capacitor and the potential Vl according to the period of the applied signal, and operates to add the frequency of the tone to the photodischarge waveform of the capacitor. Further, while the switch 81!2 is connected to one end of the capacitor, the charge of the capacitor is
It is discharged through the path of the second switch, the mixing resistor, the base end, and the emitter end. However, in this method, although the mixing resistor at the base end of the bipolar transistor 140 provides a mixing waveform similar to that shown in FIG. It has a frequency component of the pitch output from the generation system 6 and a frequency component of the pitch output from the second melody generation system 7,
■ Only a waveform having two potentials, DD and VB2, appears, and therefore, the acoustic signal generated from the piezoelectric buzzer includes not only the frequency components of the pitches emitted from the first and second melody generation systems. , and also have frequency components of the sum and difference of the two, which produces a beat effect and gives the impression of audible distortion.

〔the purpose〕

It is an object of the present invention to solve such problems, to provide good sound quality to the heavy sounds generated from the piezoelectric buzzer, and to apply the conventional technology for attenuating the acoustic signals.

〔overview〕

The present invention provides a piezoelectric buzzer having a shape in which a piezoelectric member having at least two different electrodes is attached to a common diaphragm, and each of the different electrodes is driven by a signal from a different single frequency generation system. It is characterized by

〔Example〕

Hereinafter, the present invention will be described in detail based on examples.

FIG. 1 (al is a partially cut away perspective view of a piezoelectric buzzer having a shape based on the present invention, in which a diaphragm 1 is used as one electrode in common, and a piezoelectric member 2 attached to the diaphragm is Two electrodes 6 are formed on the top.Furthermore, the principle circuit diagram for driving a piezoelectric buzzer having this shape is shown in FIG.
The common diaphragm of the piezoelectric buzzer 16 is connected to the VDD level,
Different electrodes of the piezoelectric member are each driven by signals from a single frequency generation system. Therefore, in the present invention, acoustic signals having two different frequencies are not electrically mixed but are audibly mixed by a common diaphragm, so that the phase difference between the two frequencies caused by the conventional drive method is The ingredients are similar to each other, and good quality can be obtained. Furthermore, since the present invention is based on a method in which one piezoelectric buzzer is driven by signals from each frequency generation system in principle, it is not possible to attenuate the acoustic signal using the conventional current supply transistor switching method or waveform duty control method. Obviously it can be done.

Another object of the present invention is to weight a plurality of acoustic signals generated from a piezoelectric buzzer. As mentioned above, the sound pressure of the acoustic signal generated from the piezoelectric buzzer depends on the amount of charge of the piezoelectric buzzer, so the
If the areas occupied by two different electrodes are changed as shown in 1, the sound pressure will be higher for the one with a larger area, and the desired weighting can be obtained.

In the embodiment of the present invention in FIG. 1, the piezoelectric member is common and only the electrodes on the piezoelectric member are divided, but the same effect can be obtained even if the piezoelectric member is divided together with the divided electrodes. .

In addition, although the specific example in the explanation of the present invention is a case of driving at two different frequencies, when driving at six or more different frequencies, for example, when generating a main melody and two types of accompaniment sextuplets, etc. Needless to say, the number of poles 'tjL of the piezoelectric buzzer is increased or decreased in accordance with the number of different frequency generation systems.

〔effect〕

As described above, according to the present invention, since good sound quality can be given to the acoustic signal generated from the piezoelectric buzzer, it is possible to replace the dynamic speaker with the piezoelectric buzzer, and there is also a method for attenuating the generated acoustic signal. Conventional technology that does not require external parts such as capacitors can be applied as a
This makes it possible to reduce the size and cost of the entire acoustic signal generation system.

[Brief explanation of the drawing]

FIGS. 1 fal and 1 fbl are external views of a piezoelectric buzzer having a shape based on the present invention. FIG. 2 is a diagram showing the principle of driving a piezoelectric buzzer according to the present invention. Figure 3 is a structural diagram of a conventional general piezoelectric buzzer. Figure 4 (1) (bl is a general drive circuit diagram of a piezoelectric buzzer. Figure 5 (al, ' (bl is a conventional technology that attenuates the acoustic signal generated from a piezoelectric buzzer. Figure 6 (al, (BL is an example of mixing two frequencies. Fig. 7 is an example of a circuit when a conventional piezoelectric buzzer is made to produce a multitone sound. 1... Vibration plate, 2... Piezoelectric member, 3 ...electrode, 4
．． 5...Single frequency generation thread, 6.7...Single melody generation system, 8, 9.12.13...Switch, io, ii...Capacitor, 14...Bipolar transistor , 15.16...Piezoelectric buzzer. Above Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] (1) A piezoelectric buzzer characterized in that a piezoelectric member having at least two different electrodes is attached to a common diaphragm. (2) The piezoelectric device according to claim 1, characterized in that the area of at least two or more different electrodes is changed and the sound pressure of the acoustic signal driving each electrode is weighted. buzzer.