JPS58111987A - Piezo-electric type alarm - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a piezoelectric alarm using a piezoelectric vibrator.

Conventionally, in a piezoelectric alarm device using a piezoelectric vibrator, the ringing frequency is determined by the resonance frequency caused by the bending vibration of the piezoelectric vibrator, and the frequency is an extremely high simple harmonic sound of about 2 to 3 KH2, which is similar to that of a buzzer, etc. The tone was not very appropriate for an alarm.

The present invention has been made to solve the above problems,
In addition to making the frequency characteristics of the piezoelectric vibrator multimodal,
It is an object of the present invention to provide a piezoelectric alarm device that has a wide range of tones and emits an audible sound of 1KH2 or less by connecting a modulation circuit and matching the carrier frequency and sideband frequency to the resonance points of a piezoelectric vibrator. This is the purpose.

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

FIG. 1 shows a plan view of a piezoelectric vibrator, in which a piezoelectric element 1 is bonded with an adhesive to a rectangular metal plate 2 with a long side a and a short side a. The piezoelectric vibrator 4 has a similar shape to the piezoelectric vibrator 2, and is bonded to a diaphragm 3 whose peripheral portion is bound to form a piezoelectric vibrator 4 as a whole.

In a piezoelectric vibrator having such a structure, bending vibrations in the long side direction and the short side direction coexist, and the vibration frequency is related to the dimensions a and b of the metal plate 2. For example, long side a+a
a40mm.

In the case of the short side bw3Q+ua, as shown in FIG. 2, the frequency characteristic showing the relationship between the generated sound volume and the frequency f is a bimodal characteristic with two resonance points, and both resonance frequencies XI.

The interval Δf of X2 was approximately 400H2.

FIG. 3 shows a circuit for exciting the piezoelectric vibrator 4 shown in FIG. 1 with an amplitude modulated wave, and a preamplifier is configured by a transistor Trl and resistors R4, R5, and R6.

A power amplifier consisting of Darlington-connected transistors Tr2 and Tr3 is connected to the output side of this preamplifier through a resistor R1. The output side of the power amplifier (the emitter of the transistor Tr3) is connected to the primary side of the step-up transformer T via a protection resistor R4 and a bypass capacitor CI. A piezoelectric vibrator 4 is installed on the secondary side of the step-up transformer T.
and the resistor R3, which are connected in parallel with each other, and the complementary common capacitor C2 are connected in series with □0. ．． -64□1mu, □engineering 4yo1,
□Since it is proportional to the current flowing through the actuator 4, this divided voltage is positively fed back to the base of the transistor Trl via the coupling capacitor C3 to form a self-excited oscillation circuit.

In addition, the collector of the transistor Tri and the transistor Tr
2, resistors R1 and R2, and a diode DI are connected to the base of
, D2 is connected to the modulation circuit. 5 is a local oscillator.

Next, the circuit operation will be explained with reference to FIGS. 3 to 5.

The self-excited oscillation circuit applies the secondary electromotive force of the step-up transformer T to the piezoelectric vibrator 4, extracts a voltage proportional to the current flowing through the piezoelectric vibrator 4 from the resistor R3, and applies a positive voltage to the base of the transistor Tri via the coupling capacitor C3. He is returning. Therefore, this self-excited oscillation circuit performs self-excited oscillation at a frequency corresponding to the frequency XI or x2 indicating the resonance point shown in FIG. Therefore,
A self-oscillating signal having a voltage waveform as shown in FIG. 4(a) is outputted to the collector of the transistor Trl, and this signal becomes a carrier wave signal. On the other hand, the local oscillator 5 outputs a modulated wave signal 1 shown in FIG. 4(b). Here, the modulated wave signal of the local oscillator 5 (FIG. 4(b)) is transmitted through the diode D2. D1. It is applied to a modulation circuit consisting of resistors R1 and R2.

At this time, during the period 0-tl, that is, the period when the output voltage is Ov shown in FIG.
Figure 4(a)) is off when it is Ov and turned on when it is +VV, so the collector voltage of the transistor Trl is connected to the base of the transistor Tr2 by the resistor R, as shown in Figure 4(C).
1 and R2, the voltage is divided and attenuated and output.

Next, during the period from tl to t2, that is, during the period when the output voltage is +vV shown in FIG. 4(b), the diode D2 is turned on.
Since the diode D1 is turned off, the transistor Tr2
As shown in Figure 4 (C), at the base (point B) of
The voltage at the point appears as is. As described above, the fourth
The voltage at point B shown in the diagram (C) is the voltage at the transistor Tr2. Tr
After the power is amplified by step-up transformer T, the voltage is boosted by step-up transformer T, and the DC component is removed.
An amplitude modulated wave shown in is outputted and applied to the piezoelectric vibrator 4 to drive it. Here, among the frequency spectrum of the amplitude-modulated modulated output, the fundamental spectrum is the self-oscillation frequency (carrier frequency) fo and the modulated wave frequency fi, as shown in Fig. 5, the sideband frequency is 10 ohms. It becomes fi. Therefore, (the automatic oscillation frequency fO matches the resonant frequency XI (or X2) shown in Fig. 2, and one of the sideband frequencies fo±f1 matches the resonant frequency x2 (or XI). The frequency fi is the second
It may be selected to be equal to the frequency interval 4f shown in the figure.

In the above embodiments, the oscillator was described as a local oscillator, but the oscillator is not limited to this, and may be any other oscillator, or may go further and may be a self-excited oscillator formed by frequency-dividing the automatic oscillation signal of the piezoelectric vibrator 4. .

As described above, according to the present invention, the frequency characteristics of the piezoelectric vibrator are made multimodal, and a modulation circuit is connected to apply a modulated output, so that the carrier frequency and the sideband frequency are respectively changed to the piezoelectric vibrator. Since the frequency is made to match the resonance point of the vibrator, it is possible to generate an audible sound with a wide range of tones and below IKH2, and thus an alarm device with excellent audibility can be obtained.

The present invention has been variously explained above with reference to preferred embodiments, but the present invention is not limited to these embodiments, and it goes without saying that many modifications can be made without departing from the spirit of the invention. That's true.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, and FIG. 1 is a plan view of a piezoelectric vibrator, and FIG. 2 is a frequency characteristic diagram showing the relationship between the generated sound volume and frequency of the piezoelectric vibrator shown in FIG. 1. , FIG. 3 is a circuit diagram, FIG. 4 is a waveform diagram of each part, and FIG. 5 is a frequency spectrum diagram. l...piezoelectric element, 2...metal plate, 3...
・Diaphragm, 4...Piezoelectric vibrator, 5...
...local oscillator, a...long side, b...short side, XI. X2...Resonance frequency + Tri, Tr2+Tr3
...transistor, R1, R2, R3, R4,
R5, R6; -...Resistance, CI, C2, C3...
...Capacity, T...Transformer, DI, D2...
··diode. Patent application Artificial Fuji Michio (and 2 others) -W11λ1 Funeral 2 Figure U'to Figure 3 Ichiran Figure 1 and P5

Claims (1)

[Claims] 1. A piezoelectric vibrator in which a piezoelectric element and a metal plate are bonded together and whose frequency characteristics exhibit multimodal characteristics with multiple resonance points; The circuit includes a circuit that uses a self-excited oscillation signal of a self-excited oscillation circuit that performs excitation oscillation as a carrier wave, and modulates the carrier wave with a modulated wave from an oscillator, and applies a modulated output to the piezoelectric vibrator to generate the resonance. A piezoelectric alarm device characterized in that the frequency of the carrier wave is made to match one of the points, and the sideband frequency is made to match the frequency of the other resonance point.