JPH063514Y2 - Fire alarm - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of use) The present invention relates to a fire alarm that issues an alarm when the ambient temperature rises above a certain value.

(Prior Art) A conventional fire alarm detects an abnormal rise in ambient temperature by using a temperature sensing element (for example, a thermistor) as shown in Japanese Utility Model Publication No. 52-74184 and Japanese Utility Model Publication No. 52-121260. Most of them issued an alarm.

(Problems to be solved by the invention) However, according to this method, temperature detection is performed only in a very narrow range where there are elements. Especially in the case of a fire, hot air usually gathers at high places in the room due to convection, and unless such a temperature sensing element is installed on the ceiling, that is, at high places, it is already too late when the alarm is issued. There is a risk that

In other words, the conventional fire alarms have been troublesome in that the installation location must be carefully selected in order to fully exert their effects.

(Means for Solving Problems) In order to solve the above problems, the present invention provides a fire alarm that can be installed anywhere. For this reason, the present invention does not detect an ambient temperature by a temperature sensitive element to give an alarm, but installs an ultrasonic sensor for measuring the distance from the alarm body to the ceiling in addition to the temperature sensitive element. The distance measurement by the sound wave sensor is normally performed, and the measurement data is stored in advance. If a distance is measured when a fire occurs after this and hot air is filled near the ceiling, the propagation time of ultrasonic waves will be different, and the measured data will be significantly different from the previously stored normal measurement data. Be different. In the present invention, a comparison circuit is provided for detecting that the difference in the measured data exceeds a certain value, and an alarm sound is generated by the detection output from the comparison circuit.

(Embodiment) FIG. 1 is a circuit diagram of a fire alarm device according to an embodiment of the present invention, and FIG. 2 is an operation state diagram showing its operation state.

In FIG. 1, reference numeral 2 is a reference signal generating circuit, which includes an oscillator 4, a frequency dividing circuit 6, and an n-ary counter 8. The carry signal of the n-ary counter 8 is supplied to the transmission circuit 10 as the first pulse signal φ ₁ . The transmission circuit 10 is configured to output an ultrasonic wave signal in response to the input of the first pulse signal.

The first pulse signal φ ₁ is also input to the reset input R of the counter 14 via the one-shot multivibrator 12. The clock input φ of the counter 14 is supplied with the second pulse signal φ ₂ from the frequency dividing circuit 6 in the reference signal generating circuit 2 via the AND gate 16. A flip-flop (hereinafter referred to as FF) is provided in the AND gate 16.
18 output signals are input. The first pulse signal φ ₁ is input to the reset input R of the FF 18, and the AND gate 20 is input to the set input S. Then, the inverted first pulse signal φ ₁ is applied to the AND gate 20.
The output signal from the receiving circuit 22 is input. The reception circuit 22 is configured to output a reception signal (“H” signal) when receiving the ultrasonic signal emitted from the transmission circuit 10.

This one-shot multivibrator 12, counter 1
4, a round trip for counting the time taken for the ultrasonic wave emitted from the transmission circuit 10 to be reflected by an external object (for example, the ceiling) and returned to be received by the reception circuit 22 by the AND gates 16 and 20 and the FF. The time counter 26 is configured.

The count value data counted by the counter 26 is supplied to the correction circuit 28. A temperature sensor 34, which is composed of a thermistor 30 and an A / D converter 32 and detects the ambient temperature and outputs corresponding digital data, is connected to the correction circuit 28. The correction circuit 28 receives a digital signal corresponding to this temperature. It is configured to correct and output the count value from the round-trip time counter 26 based on the data. That is, this is because the propagation velocity of the ultrasonic wave in the air differs depending on the temperature, and therefore the round-trip time for the same distance will be different unless it is corrected according to the ambient temperature.

The corrected data from the correction circuit 28 is input to the latch counter 38 in the latch circuit 36. An AND gate 40 is input to the latch input terminal of the latch counter 38, and the AND gate 40 further receives a third pulse signal φ ₃ in the reference signal generating circuit 2 and a delay circuit 42.
The output signal from is inverted and input. Delay circuit 42
Is a counter 44 in which the fourth pulse signal φ ₄ from the reference signal generation circuit 2 is input to the clock input φ and the final output signal Q thereof is inverted and input to the AND gate 40, and the counter 44 is reset. An inverter 46 connected to the input R. An external switch 48 is connected to the inverter 46.

On the other hand, the count data of the latch counter 38 in the latch circuit 36 and the count data from the correction circuit 28 are input into the comparison circuit 50. The comparison circuit 50 is configured to detect a difference between the two types of count data and output an alarm signal when the difference is a certain value or more.

The alarm signal from the comparison circuit 50 is input to the AND gate 52. An output signal from the other delay circuit 42 is input to the AND gate 52, and the output signal is output together with the audible frequency signal φ ₅ from the reference signal generation circuit 2 to the alarm generator 5.
I am typing in 4.

The usage and operation of this circuit will be described below.

As shown in FIG. 2, the transmitter circuit 10 and the receiver circuit 22.
Place the alarm body so that the arrow points toward the ceiling.

At this time, the first pulse signal φ ₁ from the reference signal generation circuit 2
As a result, an ultrasonic signal is generated from the transmission circuit 10. At the same time, the FF 18 is reset and a positive single pulse is generated from the one-shot multivibrator 12 to clear the count value of the counter 14. When the output of the FF 18 becomes “H”, the second pulse signal φ ₂ is input to the clock input φ of the counter 14 via the AND gate 16 and starts counting.

When the ultrasonic waves emitted from the transmission circuit 10 are reflected by the ceiling and input to the reception circuit 22, the reception circuit 22 outputs a reception signal of “H” level. When this received signal is input to the set input S of the FF 18 via the AND gate 20, the output becomes “L”, the AND gate 16 is closed, and the counting of the counter 14 is stopped. This operation is performed every time the first pulse signal φ ₁ from the n-ary counter 8 becomes “H”.

The count value of the counter 14 is corrected by the temperature data from the temperature sensor 34 and input to the latch counter 38.

When the external switch 48 is turned on at this time, the counter 44
Is cleared and the counting of the fourth pulse signal φ ₄ is started. The counter 44 is configured to output a signal of "L" from the output Q during counting and fix the output Q to "H" until the output Q is reset again after the count of a certain time is completed. Therefore, the latch input terminal L of the latch counter 38 has a third value only during counting.
When the pulse signal φ ₃ is input and the output Q signal of the counter 44 becomes “H”, the correction circuit 2 at the rising edge of the third pulse signal immediately before the Q output signal becomes “H”.
The count data of 8 will be latched. This is because if the count data is latched in the latch circuit 36 immediately after the fire alarm is installed, the data when the user who is the heat source is present and the ambient temperature is slightly higher will be latched. This is because the data that is slightly different from the normal data when there is no person will be latched.
Therefore, in the present invention, the delay circuit 42 is provided so that the latch circuit 36 does not latch the data between the time the user installs the fire alarm and the time the user moves away.

Since the count data from the latch counter 38 and the count data from the correction circuit 28 are not different in the normal case, no alarm signal is generated from the comparison circuit 50. However, when a fire occurs and the hot air first fills the ceiling, the temperature of a part of the ultrasonic wave propagation path changes as shown in FIG. 2, so the ultrasonic wave propagation speed changes. Along with this, the count value of the counter 14 changes.

In this way, in the initial state of the fire, the correction circuit 28
The count data output from the counter differs from the count data latched by the latch counter 38. When the comparison circuit 50 detects that the difference is a certain value or more, it outputs an "H" alarm signal, and this signal is input to the alarm generator 54 via the AND gate 52 which is in the open state at this time. The alarm generator 54 issues an alarm corresponding to the audio frequency signal to notify that a fire has occurred.

(Effect of the Invention) As described above, the present invention focuses on the fact that the propagation velocity of ultrasonic waves changes depending on the temperature, and by irradiating the place where the temperature rises first (for example, the ceiling) with this ultrasonic wave in the case of a fire. By detecting the change in the propagation speed, it is possible to promptly notify the occurrence of a fire. For this reason, it is no longer necessary to place the fire alarm itself in a limited place such as the ceiling as in the past, and any place that can emit ultrasonic waves to the place where the temperature changes first during a fire, such as the ceiling, can be used anywhere. It has the advantage that it can be easily installed and that the detection sensitivity does not drop depending on the installation location.

[Brief description of drawings]

FIG. 1 is a block circuit diagram of a fire alarm according to an embodiment of the present invention. FIG. 2 is an operation state diagram thereof. 2 ... Reference signal generation circuit, 10 ... Transmission circuit, 22 ... Reception circuit, 26 ... Round trip time counter, 28 ... Correction circuit, 34 ... Temperature sensor, 36 ... Latch circuit, 42 ... Delay circuit, 48 ... External switch, 50 ... Comparing circuit, 54 ... Alarm generator.

Claims (1)

[Scope of utility model registration request] 1. A reference signal generation circuit for outputting a plurality of types of pulse signals having different frequencies, and a transmission circuit for outputting an ultrasonic signal to the outside in response to generation of a first pulse signal from the reference signal generation circuit. A receiving circuit for receiving the ultrasonic signal reflected by an external object; and a counting circuit for starting the second pulse signal from the reference signal generating circuit in response to the generation of the first pulse signal. A round-trip time counter that stops counting in response to the reception of an ultrasonic signal by the receiving circuit, a temperature sensor that detects temperature and converts it into corresponding digital data, and a count value from the round-trip time counter that is output from the temperature sensor. The correction circuit that corrects according to the digital data of and converts it to the data corresponding to the distance, and the data from this correction circuit is input to the latch input terminal. Latch circuit for latching the data from the correction circuit in response to the input of a latch signal, an external switch for supplying a latch signal to the latch input terminal of the latch circuit, and a latch for the external switch and the latch circuit. A delay circuit connected between the input terminal and the delay circuit for delaying the input of the latch signal to the latch input terminal, and comparing the data from the latch circuit and the correction circuit,
A fire consisting of a comparator circuit that outputs an alarm signal when the difference is a certain value or more, and an alarm generator that generates an alarm sound by the alarm signal from the comparator circuit and the audible frequency signal from the reference signal generating circuit. Alarm.