JPS60230295A - Compound fire sensor - 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] This invention uses an element with multiple functions to eliminate heat, smoke, flame, etc.
This invention relates to a simple fire detector that detects gas.

Conventionally, two types of fire detectors have been approved by the Japanese Fire Service Act: heat detectors and smoke detectors, and heat detectors include fixed temperature types, differential types, compensation types, etc. For example, the bimetal type used in constant temperature and differential types uses a bimetal made by laminating a low expansion metal and a high expansion metal, and when the bimetal fixed at one end receives heat, the metal with a low expansion coefficient It curves to the side, producing a displacement proportional to temperature. As a result, when the bimetal reaches a certain temperature, it closes the contacts and activates the sensor. Furthermore, there are two types of smoke detectors: photoelectric type and ionization type, and the former photoelectric type includes dimming type and scattered light type. For example, it is as shown in FIG.

Reference numeral 1 denotes a light projecting section, which includes a light source 3, a lens 4, and a light receiving element 2 that compensates for a decrease in brightness of the light source. or,
10 is a light receiving section, which includes a lens 11, an aperture 12 and a light receiving element 13.
It is made up of. Now, when the smoke 6 enters the optical path 5, the amount of light received by the light receiving element 13 decreases in proportion to the amount of smoke 6 that has entered, and when the amount of light reaches a predetermined value, the sensor is activated. Next, flame detectors are intended for early fire detection, and are recognized as fire detectors by the US UL standards and NFPA. In addition to ultraviolet rays and infrared rays, this flame detector includes a visible light sensor developed by the applicant, and the applicant has devised a device that can detect flame and smoke with a single detection element. (Japanese Patent Application No. 58-069752) On the other hand, typical gas detectors include catalytic combustion type sensors and semiconductor type sensors. For example, the semiconductor method utilizes changes in the electrical conductivity of the semiconductor due to gas adsorption and desorption phenomena that occur on the surface of metal oxides (SnOZnO, etc.).
Its structure is as shown in Figure 2. The electrodes 15 are embedded in a metal oxide semiconductor 16, one electrode is used as a heater, and the remaining electrodes are used to measure the electrical resistance of the semiconductor present between the electrodes. Here, the heater is provided to heat the semiconductor surface to a temperature (200 to 400° C.) at which gas can be easily adsorbed and desorbed. As mentioned above, there have been conventional sensors that detect heat, smoke, flame, and gas, but each one is independent and has no relation to each other, so even if these four sensors are installed, (For general households, gas detectors are only partially used due to price issues.) There are many non-fire alarms; for example, in 1981, the Tokyo Fire Department
26 installed in 1,500 objects under the jurisdiction once a year from January
According to the results of a survey of 2,152 self-fire alarm detectors, there were 7,469 non-fire alarms, and the non-fire alarm rate was 86% for smoke detectors and 14% for heat detectors. In particular, most fire alarms occur during the daytime, and human factors such as large amounts of cigarette smoke, cooking smoke, and heat account for the majority of the time, accounting for about 60%.

However, on the other hand, considering that 38,000 building fires occur annually (according to the 1980 Fire Services White Paper), approximately 50%, or 19,200, are residential fires. There is a growing need for an inexpensive fire detector that generates fewer non-fire alarms and is suitable for general residential use.

In view of the above-mentioned circumstances, the present invention is designed to be simple and suitable for general residences, and as non-fire alarm countermeasures: (1) Reduces sensitivity to gas and smoke during the daytime when there are many people.

(Heat sensitivity is assumed to be constant) (2) Transient heat, smoke, flame, and gas do not issue an alarm (86% of non-fire alarms are transient) (3) Warnings and warnings Differentiate between alarms.

The present invention provides a fire detector incorporating the above functions.

As mentioned above, most of the causes of non-fire alarms are human-induced. This invention is characterized by minimizing this effect and having a simple structure using inexpensive elements.In order to distinguish between day and night, a photoconductive element is provided (this element makes a difference when irradiated with light). 6) For example, for this element, CdS (
Cadmium sulfide) is used. This photoconductive element is used to detect flame flickering, but the flickering used for flame combustion is usually 10 to 20 Hz, and even CdS, which has a relatively slow rise response time (30 to 100 m5), can be sufficiently detected. It is. Furthermore, since this photoconductive element has a relatively slow response time, it has the advantage of being less susceptible to the effects of 2f noise caused by AC lighting and the like. Sensitivity is switched by the DC component of this photoconductive element.

That is, the sensitivity is set high at night and set low during the day.

Also, flame detection will be carried out at the exchange meeting. (Smoke detection is also possible, but this is done with the following.) Next, semiconductor oxide elements are used to detect smoke, gas, and heat, but here too a thermistor is used as a device with stable characteristics and low cost. use (A thermistor is an oxide semiconductor whose resistance is temperature dependent (generally has a negative temperature coefficient). Gas and smoke detection uses the change in thermal conductivity when the thermistor self-heats; uses the resistance change of a thermistor for ambient temperature compensation.

In other words, CdS detects flames in addition to distinguishing between day and night, and thermistors detect gas, smoke, and heat (of which heat is used for temperature compensation).
This allows one element to have multiple functions.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below with reference to drawings of embodiments.

FIG. 3 shows a block diagram of the device. 20 is a thermistor that detects heat (the one used for temperature compensation is also used for heat detection) 21 is a preamplifier, 22 is a thermistor for gas, smoke, detection, 23 is a preamplifier, and 24 is a flame detection Cd for
S (This is a device that distinguishes between day and night and switches sensitivity, and is also used for flame detection.) 25 is an AC amplifier, 25a is a flame detection signal (AC signal), 26 is a DC amplifier including a first-order delay element, and 26a is a 6 represents a DC signal corresponding to the surrounding brightness
27 is a comparator, 28 is an amplifier, 29 is a sensitivity switching circuit that switches sensitivity, and the connections 20, 22, and 24 are as follows:
It is as shown in Figure 4. 20.21.22.23.2
4 is the same as in FIG. It is important to note here that a thermistor is one of the popular temperature measuring devices, but when measuring general temperature, the current is limited to prevent the thermistor from self-heating, but it is also used for gas and smoke detection. However, in order to facilitate the detection, the temperature here is self-heated to, for example, about 150 to 180°C. A bead type thermistor with a B constant of 3400°K and a resistance value of about 8Ω at 25°C is suitable as this thermostat. A constant current circuit of 50 is used to improve the stability of detection.

51 is a DC power supply. 52.53 is a resistor, and this and 20.22 constitute a bridge circuit. 20 compensates for fluctuations in voltage and ambient temperature without coming into contact with gas or smoke.

When gas or the like reaches the vicinity of the sensing element 22, the thermal conductivity changes, so the temperature of the thermistor changes and the bridge becomes unbalanced, so that an output 23a is taken out. Further, when there is a sudden temperature rise due to a fire, the resistance of the circuit 20 changes rapidly, and this is taken out by the buffer amplifier 21. In the embodiment, it is taken out from 20, but it is also possible to detect it from 22. In this case 21 input lines 21'
Instead of connecting to point A, connect it to point B. (However, in this case, the influence of gas and smoke is also taken into account, but since the influence of changes due to heat is greater, it is possible to separate them.) Returning to the embodiment in FIG. 3, 30 is the main amplifier. In particular, for smoke, gas flames, etc. that often cause non-fire alarms, the sensitivity during the day is lower than at night.6 (The sensitivity is switched here, but the duration can also be changed.) One of the features of this detector is that it does not switch. Reference numeral 31 denotes a low-pass filter, which removes induced noise from the AC power supply, and has a cutoff frequency of about 30 Hz.

A comparator 32 generates an output 32a when the amplitude of the signal 31a exceeds a predetermined value.

33 is a pulse number detection circuit, as shown in FIG. 5(A). Moreover, FIG. 5(B) shows the waveforms of each part.

In FIG. 5(A), 60 is a differentiating circuit, 61 is a waveform shaping circuit, 62 is a preset counter, and 63 is a monostable multivibrator. Also, P is a positive power supply and P1 to P
4 is a preset input terminal for setting a predetermined number of pulses. Now, when there is an input through the comparator 32, 62
The counter counts down for each input pulse, and when the content reaches zero, it is output to the carry-out terminal E as shown in Fig. 5 (B
) A waveform as shown by 33a is output. if,
If the counter 62 does not reach zero within the set time T of the monostable multivibrator 63, it will be preset again and the terminal E will be reset.
No output appears.

Note that FIG. 5(B) shows a case where the preset input switch is set so that four clock pulses are output. With this pulse number detection circuit of 33, even if gas, smoke, flame, etc. are detected, the output will be 33. A is not emitted, and the influence of noise due to external disturbances can also be removed.

As shown in FIG. 3, 37 is a time detection circuit, and this circuit is constructed as shown in FIG.

R1-R6...resistance, cl...capacitor.

71... Diode, 72... FET transistor, 73.74... Operational amplifier, 7o1. - Transistors, P, N...Positive and negative power supplies.

Now, when 32a is not present, the FET 72 is turned on, and the input and output of the operational amplifier are connected through a small-value resistor R2 (however, R5>). is not output. Here, 32a
(However, when there is a negative logic pulse), 72 is OFF, R2 is not connected, and C1 with a large capacitance value (for example, IO
MF), and 73 becomes an integrator, that is, 73aV
s and 73b as Vo. Therefore, since the operational amplifier 74 constitutes a comparator, when Vo of 73b exceeds the threshold level determined by R3 and R4, 37a is output. This time detection circuit extracts a heat signal and outputs an output 37a if the temperature remains above a certain temperature for a predetermined period of time, so it does not detect intermittent signals. This enables highly reliable heat detection. As shown in FIG. 3, 34 is an OR circuit which outputs an output 34a if either 33a or 37a is present. 35 is 34 with a timer
In response to the input of a, an output 35a is generated for a set time and is sent to an output circuit 36. The output signal 36a sounds a buzzer or lights up an indicator light. Here, the buzzer 36a intermittently sounds as a warning. 38 is an AND circuit which emits signal 38a only when 33a and 37a are simultaneously pressed. 39 is a timer, and 40 is an output circuit, which uses an output signal 40a to sound a buzzer or turn on an indicator light. Here, 40a
This causes the buzzer to continuously sound as an abnormality alert. A warning is issued when one of heat, gas, smoke, or flame is detected, but an abnormality alarm is issued when two or more are detected, making this an extremely reliable fire detector. I can do it.

As described above, according to the present invention, the detection sensitivity for flame, gas, and smoke automatically becomes lower during the day when there are many people than at night, and it does not work with temporary heat, smoke, gas, and flame. When an element is detected, a warning is issued, and when two or more elements are detected, an abnormality alarm is issued, making it highly reliable.Furthermore, the circuit configuration can be realized by a combination of extremely simple elements, making it inexpensive and non-intrusive. It can be highly effective as a composite fire detection device suitable for use in general homes where there are very few fire alarms.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing a conventional dimming type sensor, Fig. 2 is an explanatory diagram showing a conventional semiconductor type gas detector, Fig. 3 is a block diagram showing an embodiment of the present invention, and Fig. 4 is an explanatory diagram showing a conventional semiconductor gas detector. Block diagrams showing how to connect heat detectors, gas and smoke detectors, and flame detectors;
FIG. 5A is a block diagram of the pulse number detection circuit, FIG. 5B is an explanatory diagram of the output waveform, and FIG. 6 is a wiring diagram of the time detection circuit. 201 thermistor, 21 preamplifier, 21 preamplifier output, 22 thermistor, 23 preamplifier, 23a
Preamplifier output, 24 sensitivity switching, 24aCdS output,
25 AC amplifier, 25a AC amplifier output, 26 DC amplifier, 26a DC amplifier output, 27 comparator,
28 Amplifier, 29 Sensitivity switching circuit 30 Main amplifier, 3
1 low pass filter, 31a LPF output, 32 comparator, 32a comparator output, 33 pulse number detection circuit, 33a pulse input number detection circuit output, 34 0R circuit, 34a OR circuit output, 35 timer,
35a timer output, 36 output circuit, 36a output signal (buzzer sound, indicator light lit), 37 time detection circuit, 3
7a time detection circuit output, 38 AND circuit, 38aAN
D circuit output, 39 Timer, 40 Output circuit, 40
Buzzer 50 constant current circuit, 51 DC power supply, 52 resistor, 53 resistor, 60 differentiation circuit, 61 waveform shaping circuit,
61a waveform shaping circuit output, 62 preset counter, 63 monostable multivibrator, 63a monostable multivibrator output, 70 transistor, 71 diode, 72 FET)-ransistor, 73 operational amplifier, 74 operational amplifier P1 to P4 preset input terminal R1-R6 resistor C1 Capacitor PN Positive and Negative Power Supply Patent Applicant Hirotaka Seki Takashi Kataishi Part 1 and 2 '' 3rd ton 1

Claims (6)

[Claims] (1) A first sensing element that responds to changes in incident light, a second sensing element that responds to changes in thermal conductivity, and a third sensing element that responds to changes in incident heat; A circuit that distinguishes flame, gas, and smoke from the amplitude of the output of the first detection element and the second detection element and the number of pulses thereof, and a circuit that distinguishes between flame, gas, and smoke from the amplitude of the output of the third detection element and its duration. A fire detection device comprising a discrimination circuit, a sensitivity switching circuit that changes the sensitivity of the discrimination circuit according to the magnitude of the DC component output of the first detection element, and a circuit that issues an alarm output. (2) The fire detection device according to claim (1), wherein the first detection element is a photoelectric conversion element. (3) The fire detection device according to claim (1), wherein the second and third detection elements are resistors having significant temperature dependence. (4) Claim (1) or (3) characterized in that the second and third sensing elements are the same.
Fire detection device described in ). (5) Claims characterized in that the sensitivity switching circuit is a circuit that increases the sensitivity of the non-thermal discrimination circuit when the magnitude of the DC component output of the first sensing element is less than a predetermined value. The fire detection device described in paragraph (1). (6) The fire detection device according to claim (1), wherein the alarm output is divided into a case where - element is detected and a case where two or more elements are detected.