JP3121250B2 - Alarm sound device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an alarm sound device for use in a local sound device or the like used in a fire alarm system, and more particularly to an alarm sound device that supplies a pulse signal to a piezoelectric element to make a sound.

[0002]

2. Description of the Related Art Conventionally, a bell has been generally used as an area sound device for a fire alarm system. However, in recent years, a piezoelectric buzzer has been used because current consumption can be greatly reduced. Are being considered. FIG. 7 shows a conventional driving device for a piezoelectric element for a buzzer, which comprises a pulse generating circuit 20 and a driving circuit 21. The pulse generating circuit 20 uses a comparator 23 to simplify the circuit configuration. The plus input terminal of the comparator 23 has a resistor R2
A reference voltage determined by 0 and R21 is set. The minus input terminal of the comparator 23 is provided with an integrating circuit of a resistor R24 charged and discharged by the comparator output and a capacitor C20, and inputs a charging / discharging voltage of the capacitor C20. A feedback resistor R22 is connected between the plus input and the output, and a load resistor R23 is connected between the output of the comparator 23 and the power supply line.

When the power supply voltage Vcc is applied to the pulse generation circuit 20, an H level is first output from the comparator 23, and the reference voltage by the voltage division of the resistors R20 and R21 is set to a slightly higher level by the feedback resistor R22. . Further, the charging of the capacitor C20 is started via the resistor R24, and when the charged voltage reaches a reference voltage set to a slightly higher level, the output of the comparator 23 is inverted to the L level. When the output of the comparator is inverted to the L level, the capacitor C20 switches from the previous charging to discharging.

At this time, the reference input of the comparator 23 is pulled down to a slightly lower level by the feedback resistor R22. When the discharge voltage of the capacitor C20 falls below this level, the output of the comparator 23 returns to the H level again. Invert. Hereinafter, this operation is repeated. As a result, the comparator 23 generates a rectangular wave pulse having a period determined by the time constant of the capacitor C20 and the resistor R24,
A drive pulse voltage is applied to the piezoelectric element 22 via the drive circuit 21 to cause the piezoelectric element 22 to sound.

The piezoelectric element 22 has a structure in which a dielectric is sandwiched between electrodes, and emits sound by utilizing the effect of mechanical distortion of the dielectric when a drive voltage is applied between the electrodes. The piezoelectric element 22 generally has a higher impedance than a speaker, and is therefore a voltage-driven element.

[0006]

However, since a piezoelectric element provided in a general electric appliance is driven by a pulse signal of a constant frequency generated from such a conventional pulse generating circuit and sounds, a fire alarm system is provided. If such a pulse generation circuit is used as it is in an alarm sound device used for an alarm sound device, etc., it cannot be distinguished from the sound of the alarm sound device, and the alarm function as the alarm sound device may not be achieved. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide an alarm sound device that can emit a sound unique to the alarm sound device by using a piezoelectric element.

[0008]

In order to achieve this object, the present invention is configured as follows. Note that reference numerals in the drawings of the embodiment are also shown. Output signal level is timed at regular intervals
Waveform generation that outputs a waveform signal that changes approximately linearly on the axis
Circuit 7 and the level of the waveform signal output from the waveform generation circuit 7
Variable frequency pulse whose frequency changes at regular intervals according to
A variable frequency circuit 8 for generating a pulse train;
And a piezoelectric element for supplying a pulse train.
The variable frequency range of the path 8 and the resonance frequency of the piezoelectric buzzer 6
In the alarm sound device that is set in a predetermined frequency range as a center , the waveform generation circuit 7
Apply the reference voltage to the output terminal and connect the output in feedback,
Comparator output to negative input terminal of comparator 9
The integration voltage of the integration circuit charged and discharged by
A configuration to output the divided voltage as the waveform signal, the variable
The frequency circuit 8 is connected to a positive input terminal of the comparator 10.
Input the waveform signal and connect the output by feedback.
The comparator output is connected to the negative input terminal of
Apply the integration voltage of the integration circuit that is charged and discharged
To output a variable frequency pulse train from the output of the data 10
And the waveform generation circuit 7 and the variable frequency circuit 8
In the meantime, the output current of the waveform signal is required by the variable frequency circuit 8.
Of the current amplification factor hfe
It is characterized in that a resistor circuit is provided.

The integrating circuit of the waveform generating circuit 7
Fast charge slow discharge cycle with small time constant and large discharge time constant
It is composed of roads.

[0010]

According to alarm sound device of the present invention, such as this, the ringing sound of the buzzer, the ringing tone with the change of specific sounds that varies continuously frequency treble from constant period, for example, Bass Therefore, even if there is a sound of a buzzer provided in a general electric appliance, the sound of the alarm sound device can be clearly distinguished, and the occurrence of an emergency such as a fire can be reliably left.

[0012]

FIG. 1 is a circuit block diagram of a district sound apparatus to which the present invention is applied. In the district audio system 1,
A power supply circuit 2, a pulse generation circuit 4, a piezoelectric element drive circuit 5, and a buzzer piezoelectric element 6 are provided. The local sound device 1 has terminals 3a and 3a connected to a control line 3 drawn from a receiver.
3b. Lines from the terminals 3a and 3b are connected to the power supply circuit 2.

The power supply circuit 2 includes a diode bridge for making the connection polarity of the control line 3 to the terminals 3a and 3b non-polar, a pulse generation circuit 4 and a piezoelectric element drive circuit 5.
And a voltage conversion circuit for supplying specific power supply voltages Vcc1 and Vcc2 to the power supply. A predetermined control voltage, for example, DC, is applied to the control line 3 when a fire is determined by the receiver.
24V is supplied.

The power supply circuit 2 is connected to the DC
24V is supplied to the piezoelectric element drive circuit 5 as the power supply voltage Vcc2. Also, 24 V supplied by the control line 3 is changed to, for example, 5 V
And supplies the power to the pulse generation circuit 4 as the power supply voltage Vcc1. The pulse generation circuit 4 outputs to the piezoelectric element drive circuit 5 a variable frequency pulse train whose frequency changes at regular intervals, as will be described later.

The piezoelectric element drive circuit 5 includes a pulse generation circuit 4
A driving pulse voltage corresponding to the power supply voltage Vcc2 is supplied to the piezoelectric element 6 by a switching operation based on a pulse train generated from the piezoelectric element 6, and a mechanical operation is performed when the driving voltage is applied to the dielectric material sandwiched between the electrodes of the piezoelectric element 6. Make a sound by using the occurrence of a natural distortion. FIG. 2 is a circuit diagram of a specific embodiment of the pulse generation circuit 4 provided in the district sound apparatus 1 of FIG.

In FIG. 2, the pulse generating circuit 4 comprises a waveform generating circuit 7 and a variable frequency circuit 8, both of which are connected by a transistor circuit 11. The waveform generation circuit 7 has a comparator 9. A reference voltage Vr obtained by dividing the resistances R1 and R2 is applied to the + input terminal of the comparator 9, and at the same time, a feedback resistance R3 is connected from the output.

The terminal voltage of the capacitor C1 in the integrating circuit (charge / discharge circuit) of the resistor R4 connected to the output of the comparator 9 and the capacitor C1 is connected to the negative input terminal of the comparator 9 via the resistor R5. . Further, a series circuit of a resistor R6 and a diode D is connected in parallel with the resistor R4. The series circuit of the resistor R6 and the diode D constitutes a quick charging circuit for rapidly charging the capacitor C1 when the output of the comparator 9 becomes H level. On the other hand, the output of the comparator 9 is H
A slow discharge circuit is configured to gradually discharge the charging voltage of the capacitor C1 when the level is inverted from the L level to the L level according to a time constant determined by the resistor R4 and the capacitor C1.

The operation of the waveform generation circuit 7 is based on the power supply voltage Vcc1.
Is applied, first, the capacitor C1 is in a discharged state, and the reference voltage Vr with respect to the + input terminal of the comparator 9 is applied.
Is large, the comparator 9 outputs an H level signal. When the comparator 9 outputs an H level, the reference voltage Vr is set to a slightly higher level by the feedback resistor R3. Further, the capacitor C1 is rapidly charged via the resistor R6 and the diode D.

When the charging voltage of the capacitor C1 reaches the reference voltage Vr set to a slightly higher level, the output of the comparator 9 is inverted to L level. With the output inversion to the L level, the + of the comparator 9 is set via the feedback resistor R3.
The input level to the input terminal is pulled down to a level slightly lower than the reference voltage Vr. In the state of the L level output of the comparator 9, the charged voltage of the capacitor C1 is discharged through the resistor R4 with a predetermined time constant, and decreases substantially linearly.

The charging voltage of the capacitor C1 is equal to the feedback resistance R3.
When the voltage falls below the voltage of the + input terminal of the comparator 9 which is pulled in, the comparator 9 is again inverted to the H level, and the capacitor C1 performs rapid charging via the resistor R6 and the diode D. And such a comparator 9
The charging operation and the discharging operation associated with the H level output and the L level output are periodically repeated.

The output of the waveform generating circuit 7 is the charge / discharge voltage of the capacitor C1, and its waveform increases from VL to VH by rapid charging as shown in FIG.
It becomes a waveform that drops from H to VL. Next, the variable frequency circuit 8 of FIG. 2 will be described. The variable frequency circuit 8 has a comparator 10. The + input terminal of the comparator 10 is biased by the divided voltage by the resistors R9 and R10, and the emitter of the PNP transistor 12 provided in the transistor circuit 11 is connected via the resistor R8. P
The base of the NP transistor 12 is connected to the capacitor C1 which is the output of the waveform generation circuit 7.

The comparator 10 of the variable frequency circuit 8
The terminal voltage of the capacitor C2 in the integrating circuit in which the resistor R12 and the capacitor C2 are connected in series to the output of the comparator is connected to the input terminal. Further, a feedback resistor R11 is connected to the + input terminal of the comparator 10 from the comparator output, and a load resistor R13 is connected to the comparator output from the power supply line.

The operation of the variable frequency circuit 8 is based on the power supply voltage Vcc.
1 is supplied from the waveform generation circuit 7 through the PNP transistor 12 of the transistor circuit 11 in the state shown in FIG.
A waveform signal as shown in (A) is input as an input signal Vin. The input signal Vin changes linearly at a constant period T1 as shown in FIG. 3A, which means that the reference voltage for the + input terminal of the comparator 10 changes with time.

Here, the time constant τ2 determined by the resistor R12 and the capacitor C2 of the integrating circuit provided in the variable frequency circuit 8 is sufficiently larger than the time constant τ1 determined by the resistor R4 and the capacitor C1 of the integrating circuit provided in the waveform generating circuit 7. I'm making it smaller. Therefore, in response to the temporal change of the waveform signal Vin of FIG. 3A with respect to the + input terminal of the comparator 10, the charging of the capacitor C2 via the resistor R12 according to the H level output and the L level output of the comparator 10 and By discharging,
As shown in FIG. 3B, the comparator 10 outputs the waveform signal Vin.
As the output signal Vout, a pulse train whose cycle is continuously shortened in accordance with the decrease of the pulse width, that is, a pulse train which continuously changes from the low frequency to the high frequency over the period T1 is output.

Here, while the time constant τ1 determined by the resistor R4 and the capacitor C1 of the integrating circuit provided in the waveform generating circuit 7, the time constant τ2 of the resistor R12 and the capacitor C2 of the integrating circuit provided in the variable frequency circuit 8 is sufficient. small. For example, the period T1 of the waveform signal of the waveform generation circuit 7 is, for example, 0.1 to
It is sufficiently long as 3 seconds, and the frequency is 10 Hz or less.
On the other hand, the variable frequency pulse train determined by the time constant τ2 of the variable frequency circuit 8 has a frequency range of several hundred Hz to 5 kHz, for example.

The range of the frequency in the variable frequency circuit 8 according to the present invention is determined in consideration of the resonance frequency of the piezoelectric element 6 shown in FIG. FIG. 4 shows frequency characteristics of the piezoelectric buzzer 6 of FIG. The piezoelectric buzzer 6 has a structure in which a dielectric is sandwiched between electrodes, and has a mechanical resonance frequency. The resonance characteristic for this frequency has a peak at the resonance frequency f1 as shown in FIG. Furthermore, the resonance characteristics of the piezoelectric element 6 change according to the ambient temperature, the variation of components, and the like.

Therefore, in the variable frequency circuit 8 of FIG. 2, if the resonance frequency at a reference room temperature of 20 ° C. is f1 as shown in FIG. The frequency of the pulse train is changed by the variable frequency circuit 8 so as to include the range of ± Δf reduced by%. That is, the lowest frequency of the variable frequency circuit 8 is, for example, a frequency f21 lower than the resonance frequency f1 by Δf, and the highest frequency when the frequency is changed is a frequency f22 higher than the resonance frequency f1 by Δf.

As described above, the resonance characteristic of the resonance frequency f1 at the reference room temperature of 20 ° C. is ± Δf from the resonance frequency f1, that is, the frequency range f21 to f10 which is 10% lower than the peak level.
By varying the frequency of the pulse train so as to include f22, even if the resonance frequency of the piezoelectric element 6 deviates from the frequency f1 in FIG. be able to.
Note that the range of ± Δf can be appropriately set in consideration of the ambient temperature, the variation of components, and the like.

Therefore, such a variable frequency circuit 8
By setting the above frequency range, the piezoelectric element 6 can always be caused to ring at a frequency including the resonance frequency without being affected by the ambient temperature, the variation of the components, and the like, which is 90 dB or more required for the district acoustic device of the present invention. The sound volume can be reliably ensured. Referring to FIG. 2 again, by providing a PNP transistor 12 as a transistor circuit 11 provided between the waveform generating circuit 7 and the variable frequency circuit 8, the input current required for the operation of the variable frequency The base current which becomes 1 / a of the amplification factor hfe is supplied to the waveform generation circuit 7.
, The waveform generating circuit 7 located at the preceding stage is not affected by the operation of the variable frequency circuit 8 at the subsequent stage, and the circuit operation can be stabilized.

If the transistor circuit 11 is not provided, the charging / discharging operation of the capacitor C1 of the waveform generating circuit 7 is affected by the input current of the variable frequency circuit 8, so that a stable waveform cannot be generated. Further, the setting of the frequency range depending on the resonance characteristics of the piezoelectric element 6 in FIG. 4 in the variable frequency circuit 8 is performed by appropriately adjusting the value of the resistor R8 provided at the + input of the comparator 10 to determine the frequency range appropriately. Can be.

FIG. 5 shows another embodiment of the pulse generating circuit 4 of FIG. 1, which is characterized in that the PNP transistor 12 provided in the transistor circuit 11 of FIG. Even in the case where the NPN transistor 13 is replaced, it is sufficient that the base current of the DC current amplification factor hfe is supplied from the waveform generation circuit 7 to the input current required for the variable frequency circuit 8, so that the variable frequency circuit 8 Can reliably prevent the waveform generation circuit 7 from being affected by the operation described above, thereby stabilizing the circuit operation.

In the embodiments shown in FIGS. 2 and 5, a fast charging and slow discharging circuit is used for the waveform generating circuit 7, but the present invention is not limited to this. For example, except for the series circuit of the rapid charging diode D and the resistor R6 of the waveform generating circuit 7, the time constant of the charging / discharging circuit composed of the capacitor C1 and the resistor R4 is appropriately set so that different timbres of the timbre are produced. Can be issued.

Further by serially connecting the diode to flow only charge current to the resistor R4 in series with the capacitor C1 of the waveform generation circuit 7, to be set individually discharging time constant and the charging time constant, for example, FIG. 6 Alternatively, a waveform signal that becomes an arbitrary triangular wave may be generated. Needless to say, the waveform generating circuit 7 is not limited to the circuits shown in FIGS. 2 and 5 using a charge / discharge circuit, and uses a function generator, a ROM using stored waveform data, Various circuits, such as those utilizing repetition of down-counting, can be used.

Further, as the transistor circuit 11, PNP
Although the example of the transistor and the NPN transistor has been described,
Any transistor circuit may be used as long as the output current of the waveform generation circuit 7 can be reduced to a DC current amplification factor hfe by 1 with respect to the input current required by the variable frequency circuit 8. Further, although a comparator is used for the waveform generating circuit 7 and the variable frequency circuit 8 to simplify the circuit configuration, the present invention is not limited to this, and an appropriate waveform generating circuit and variable frequency circuit can be used.

Further, in the above embodiment, the district sound device is taken as an example, but the present invention is not limited to this.
It can be used as it is for the main sound device provided in the receiver and other appropriate alarm sound devices.

[0036]

As described above, according to the present invention, a variable frequency pulse train whose frequency changes at a constant cycle is supplied to a piezoelectric element, and a unique frequency that repeatedly changes in a range from a low tone to a high tone or a high tone to a low tone is supplied. Can sound clearly, and the buzzer used for general appliances that emits a continuous sound at a certain frequency can be clearly distinguished from the buzzer sound of the alarm sound device. It is possible to reliably report occurrence of a situation.

Further, since the frequency of the pulse train is changed within a predetermined frequency range centered on the resonance point of the piezoelectric element, even if the resonance frequency of the piezoelectric element is shifted depending on the ambient temperature, the variation of parts, etc. The sound of the piezoelectric element can be generated in a frequency range that always passes through the resonance frequency, and the sound is always generated using the resonance frequency portion of the piezoelectric element, so that a sufficient sound volume due to the sound of the piezoelectric element can be ensured.

[Brief description of the drawings]

FIG. 1 is a circuit block diagram of a district acoustic device of the present invention.

FIG. 2 is a circuit diagram showing an embodiment of the pulse generation circuit of FIG. 2;

FIG. 3 is a time chart showing operation waveforms of FIG. 2;

FIG. 4 is an explanatory diagram of a variable frequency range with respect to resonance characteristics of the piezoelectric element of FIG.

FIG. 5 is a circuit diagram showing another embodiment of the pulse generation circuit of FIG. 2;

FIG. 6 is an explanatory diagram of another waveform signal generated by the waveform generation circuit of the present invention.

FIG. 7 is a circuit diagram of a conventional driving device for a piezoelectric element for a buzzer.

[Explanation of symbols]

 1: district acoustic device 2: power supply circuit 3: control line 4: pulse generation circuit 5: piezoelectric element drive circuit 6: piezoelectric element 7: waveform generation circuit 8: variable frequency circuit 9, 10: comparator 11: transistor circuit 12: PNP Transistor 13: NPN transistor

──────────────────────────────────────────────────続 き Continuation of front page (58) Field surveyed (Int. Cl. ⁷ , DB name) G08B 23/00 G08B 17/00 G08B 27/00 G10K 9/12 G10K 9/122

Claims (2)

(57) [Claims] 1. An output signal level on a time axis at every fixed period.
Generator that outputs a waveform signal that changes approximately linearly
And the level of the waveform signal output from the waveform generation circuit.
To generate a variable frequency pulse train whose frequency changes
Generating a variable frequency circuit, and the variable frequency pulse train.
And a piezoelectric element for supplying the variable frequency generating circuit.
The variable frequency range is centered on the resonance frequency of the piezoelectric element.
In the alarm sound device set to a predetermined frequency range, the waveform generating circuit is connected to a positive input terminal of a comparator.
Apply the reference voltage and connect the output by feedback.
To the negative input terminal of the
Apply the integrated voltage of the discharged integrating circuit, and
Wherein the variable frequency circuit is configured to output the waveform signal as a plus signal input terminal of a comparator.
The waveform signal is input to the
The comparator output is connected to the negative input terminal of the comparator.
The integration voltage of the integration circuit, which is charged and discharged by
Output the variable frequency pulse train from the output of the comparator.
In addition, between the waveform generating circuit and the variable frequency circuit,
The output current of the waveform signal is required by the variable frequency circuit.
To reduce the DC current amplification factor to 1 / fe
An alarm sound device comprising a transistor circuit . 2. The alarm sound apparatus according to claim 1, wherein the integration circuit of the waveform generation circuit has a small charging time constant and discharges the signal.
An acoustic device characterized by a fast charging slow discharging circuit having a large time constant .