JPH0325266Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial field of application> This proposal relates to a composite fire detector that is activated by four phenomena: flame, heat, smoke, and gas.

<Prior Art> There are two types of fire detectors conventionally used in Japan (approved by the Fire Service Act): heat detectors and smoke detectors. Heat detectors include constant temperature type, differential type, compensation type, 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.
When a bimetal fixed at one end receives heat, it curves toward the metal with a lower coefficient of expansion, causing a displacement proportional to the 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, the light emitting unit 31 is of a dimming type as shown in FIG. The section 40 includes a lens 41, an aperture 42, and a light receiving element 43. Now, when smoke 36 enters the optical path 35 emitted from the light projector 31, the amount of light received by the light receiving element 43 decreases by an amount proportional to the amount of smoke 36 that has entered, and the amount of light decreases to a predetermined value. The sensor is activated when it reaches . Secondly, flame detectors are intended for early fire detection, and are recognized as fire detectors by the US UL standards and NFPA. In addition to an ultraviolet sensor and an infrared sensor, this flame detector includes a visible light sensor that the applicant previously proposed, and is a device that can detect flame and smoke with a single detection element (patent application). (Sho 58-69752).

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 a semiconductor due to gas adsorption and desorption phenomena that occur on the surface of metal oxides (SnO ₂ , ZnO, etc.), and its structure is as shown in Figure 6. be. The electrodes 55 are embedded in a metal oxide semiconductor 56, one of which is used as a heater, and the other of which is used to measure the electrical resistance of the semiconductor 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, conventionally,
There were separate sensors for detecting heat, smoke, flame, and gas, but they were independent and had no relation to each other.

<Problems to be solved by the invention> In view of the above-mentioned circumstances, the purpose of the present invention is to provide a simple composite fire detector that can detect heat, smoke, flame, and gas and can be applied to general houses. That is.

<Means for Solving the Problems> The present invention comprises a first sensing element that responds to changes in incident infrared radiation, a second sensing element whose electrical conductivity changes due to gas adsorption/desorption phenomena, and the first sensing element that responds to changes in incident infrared rays. A pulse stretcher stretches the output of the first sensing element for a predetermined period of time, and the output of the second sensing element is guided to two comparator circuits set to different reference voltages. a delay circuit that delays the output of the comparator circuit for a predetermined time; and a logic circuit that combines the output of the comparator circuit with a higher reference voltage with the output of the pulse stretcher and makes a logical judgment between the composite output and the output of the delay circuit. and gas,
In a fire detector that detects abnormal conditions such as smoke, flame, heat, etc., an alarm sound is made different depending on the type and degree of the abnormal state, and the lighting operation of an indicator light is made different in synchronization with the alarm sound. This is how it was done.

<Example> Shown in FIG. P and N are DC positive and negative potentials, respectively. Reference numeral 10 denotes a semiconductor element for sensing smoke and gas, for example, a metal oxide semiconductor such as _SnO2 . 21 is a pyroelectric element that senses heat and flame.

20 is a temperature correction sensing element, for example a thermistor. R1 to R11 are resistors (R2, R3, R
4, R9 is a variable resistor) C1 is a capacitor, D
1, D2, D3 are diodes, Tr ₁ , Tr ₂ are NPN
type transistor, LD is an indicator light, BZ is a buzzer, 1, 2, 3, 4, 5, 6 are comparators, 7 is a delay circuit, 8, 9, 11, 12, 13, 14, 18, 1
9 and 20 are NAND circuits, 10 and 15 are AND circuits, 16 is an astable multivibrator, and 17 is a pulse stretcher. This operation will now be explained. When smoke or gas comes into contact with the element 10, due to an adsorption/desorption reaction with the gas on the element surface, the electrical conductivity of the element 10 increases, that is, the resistance decreases as shown in FIG. 2I.
As the resistance decreases, the potential V1 at point A increases to a value determined by 10 and R1. 1 is a comparator whose reference voltage is set to an arbitrary value V3 by adjusting a variable resistor R3. Now, when V1 becomes higher than V3, comparator 1
An output 1' is generated. Here, since R6 and C1 constitute a delay circuit, the voltage V6 changes as shown in FIG. Therefore, by inputting V6 to another comparator 4 and appropriately setting its reference voltage V7 using R7 and R8, the output Vc of the comparator 4 can be delayed as desired. Its function is to prevent alarms from being triggered due to gases generated during spraying or cooking, cigarette smoke, etc. However, when a large amount of gas suddenly ejects and diffuses,
V1 will rise rapidly, but due to the delay effect of R6 and C1, Vc will occur immediately, potentially leading to a serious accident. Here, R2 and R3 are determined so that V2>V3, and when V1>V2, the output 2' of the comparator 2 is output and VD is generated without delay. That is, if a large amount of gas or smoke is generated, the alarm circuit is activated immediately.

In addition, when flame or heat is generated (when no smoke or gas is generated), charges essentially based on spontaneous polarization appear on the surface of the pyroelectric element 21, but in the atmosphere, floating charges appear. Therefore, it is neutralized and no apparent charge is observed. In this state, when the surface of the pyroelectric element 21 is irradiated with infrared rays (heat rays) caused by flame, heat, etc., the charge is absorbed and the temperature of the pyroelectric element 21 increases. The magnitude of this spontaneous polarization decreases as the temperature rises, and the magnitude of the spontaneous polarization of the pyroelectric element 21 changes instantaneously due to temperature changes. However, it takes time for this surface charge to reach equilibrium, and it remains in a non-equilibrium state for some time. This unbalanced surface charge is detected as a voltage.
For example, if the pyroelectric element 21 receives incident heat as shown in FIG. 2a, the output will be as shown in FIG. 2b. Therefore, when there is no temperature change, this pyroelectric element 21 has only the DC bias voltage shown in FIG. 2b. Of course, when the temperature change is gradual, the change in the output signal is also gradual, and no output is output from the comparator circuit 6.

Next, the operation of 20 will be explained.

When the ambient temperature increases (e.g. due to seasonal changes), 1
0 is affected by this, for example in the case of SnO ₂ , the fourth
As shown in the figure, the element resistance decreases. Therefore, 1,2
If the reference voltage is fixed, in summer when the ambient temperature is high, the sensitivity will increase due to the increase in V1, and in some cases, 1' will occur even when no smoke or gas is generated, causing false alarms. Become. In order to correct the influence of this ambient temperature, a thermistor (negative characteristic), for example, is used as the temperature sensing element 20. The resistance-temperature characteristics of this thermistor are similar to those of the element 10, and the resistance decreases as the temperature increases. When the ambient temperature rises, V1 rises, and the potential at point B rises accordingly, causing V3 and V2 to rise. Therefore, by optimally selecting the 20 characteristics, the ambient temperature can be corrected. This thermistor 20 is a necessary element for accurately detecting gas and smoke without false alarms, but in the present invention, this ambient temperature correction thermistor is also intended to be used for detecting heat in the event of a fire.

Fires generally generate poisonous gases and smoke, so 10 is effective, but 10 does not work if the concentration of smoke or gas is low due to the influence of wind or a fire in a neighboring house. However, when the temperature rises due to heat, the resistance of 20 decreases as described above, and the potential at point B increases. Therefore, if the reference voltage V4 of the comparator 3 is appropriately determined by the resistor R4 in consideration of the surrounding environment, etc., and the output 3' is generated at a temperature of 60°C, for example, if the temperature is 60°C or higher, When this happens, VD is immediately output without delay and the alarm circuit is activated.
Here, the functions of diodes D1, D2, and D3 are as follows:
Outputs 3', 2', and 17' are output from comparators 2 and 17', respectively.
This is to prevent it from being affected by the equivalent output resistance (not shown) of the pulse stretcher 17 and pulse stretcher 17, and is provided to stabilize VD.

Next, the output circuit will be explained.

Reference numeral 7 denotes a delay circuit for preventing malfunctions until the initial stabilization of the semiconductor element, and is composed of R and C2, for example, as shown in Figure 7a, and its characteristics are as shown in Figure 7b. . This delay circuit prevents false alarms when the power is turned on or turned off. Until the initial stabilization, the output 7' does not exceed the threshold value V7 of the comparator 5 determined by the resistors R7 and R8, so VL is in the "L" state. FIG. 8a shows an astable multivibrator, which is composed of an IC timer called NE555, for example. Also, b in the figure shows the waveform of the output 16'. Here, until initial stabilization, the pulse interval was set in synchronization with the output 16' of the astable multivibrator 16, whose pulse interval can be set as shown in equations 1 and 2 using resistors RA and RB and capacitor C4.
The indicator light LD is turned on and off by the output 14' of the NAND circuit 14. On the other hand, the buzzer BZ does not sound because the output 15' of the AND circuit 15 is "L".

Output High t ₁ = 0.693 (RA + RB) C4 ... (1) Output Low t ₂ = 0.693RBC4 ... (2) After the semiconductor element 10 is initially stabilized, gas or smoke gradually spreads and the semiconductor element 10 captures them. In this case, first, the potential V1 at point A in FIG. 1 rises and when V1>V3 compared to the reference voltage V3 of comparator 1, the output 1' becomes "H" and VL becomes "H" after initial stabilization.
Therefore, the output 1 of the NAND circuit 14 synchronized with the output 16' of the astable multivibrator 16
4', the indicator light LD blinks regularly until the potential V6 at point C becomes V6>V7 compared to the reference voltage V7 of the comparator 4 and the output Vc is generated, and the output of the AND circuit 15 synchronizes with this. Buzzer by 15'
BZ emits regular intermittent sounds. Furthermore, if Vc occurs after a certain time determined by R6 and C1,
The output 14' of the NAND circuit 14 and the output 15' of the AND circuit 15 are not synchronized with the output 16' of the astable multivibrator 16, so the indicator light LD lights up and the buzzer goes off.
BZ sounds continuously.

On the other hand, as the gas or smoke spreads rapidly, the potential V1 at point A increases, and compared to the reference voltage V2 of comparator 2, V1
> V2 and the output VD occurs (at this time, the output 1' of the comparator 1 becomes "H", and after a certain period of time the output Vc of the comparator 4 also becomes "H") and due to a gradual temperature rise. When the potential VB at point B in the temperature correction sensing element 20 rises and becomes VB > V4 compared to the reference voltage V4 of the comparator 3 and VD occurs,
The output 14' of the NAND circuit 14 and the output 15' of the AND circuit 15 are not synchronized with the output 16' of the astable multivibrator 16, the indicator light LD lights up, and the buzzer BZ sounds continuously. In addition, when flame or heat is generated, the output 21' of the pyroelectric element 21 is generated,
When this output 21' becomes larger than the reference voltage V9 of the comparator 6, an output 6' is produced. Since the output 6' is a discontinuous pulse signal, in order to stably operate the indicator light LD and buzzer BZ, the pulse stretcher 17 and astable multivibrator 16 shown in FIG. The pulse width of the output 16' of the vibrator 16 prevents short pulses from occurring, thereby ensuring stable operation of the indicator light LD and buzzer BZ. 16',1 at this time
The output waveform of 7' is shown in FIG. Therefore, the irregular output 17' is connected to the output 14' of the NAND circuit 14.
The output 15' of the AND circuit 15 is synchronized, and the indicator light LD
points are deducted irregularly, and the buzzer BZ is synchronized with this,
Sounds irregularly. The output waveforms of each part at this time are shown in FIG. In the present invention, an electronic buzzer or the like is used for this alarm sound, but it is not limited to this, and it is also possible to broadcast the type of abnormality by voice synthesis.

<Effects of the present invention> As mentioned above, the composite fire detector of the present invention uses inexpensive and highly reliable semiconductor elements and pyroelectric elements.
It can detect gas, smoke, flame, and heat with extremely high accuracy. Furthermore, the alarm sound generated varies depending on the type and degree of abnormal conditions such as gas, smoke, flame, heat, etc., and the indicator light is operated in synchronization with the alarm sound, so light and sound can be used to identify the type of abnormal phenomenon and emergency. It has an unprecedented feature in terms of disaster prevention in that it can quickly notify the extent of the disaster, making it easier to respond to abnormal phenomena without causing unnecessary confusion. Therefore, this device can be highly effective as a detector suitable for general homes.

[Brief explanation of the drawing]

Figure 1 is a block diagram of the present invention, Figure 2,
a and b are explanatory diagrams of the operation of the semiconductor element and the pyroelectric element;
Figure 3 is an explanatory diagram showing the operating characteristics of the delay circuit;
The figure is an explanatory diagram showing the resistance-temperature characteristics of a temperature sensing element, and Fig. 5 is an explanatory diagram showing a conventional dimming type sensor.
Figure 6 is an explanatory diagram of a semiconductor device, Figures 7a and b are diagrams of a delay circuit and its operation to prevent malfunctions until initial stabilization of the semiconductor element, and Figures 8a and b are astable multivibrators. circuit diagram and operation diagram,
FIG. 9 is an explanatory diagram of waveforms of the pulse stretcher, and FIG. 10 is an explanatory diagram of waveforms of various parts of the output circuit when the pyroelectric element captures flame or heat. 10... semiconductor element, 20... temperature sensing element,
21...Pyroelectric element, 1, 2, 3, 4, 5, 6...
...Comparison circuit, 17...Pulse stretcher.

Claims (1)

[Scope of utility model registration request] a first sensing element that responds to changes in incident infrared radiation, a second sensing element whose electrical conductivity changes due to gas adsorption/desorption phenomena, and a pulse stretch that stretches the output of the first sensing element for a predetermined period of time. a delay circuit that leads the output of the second sensing element to two comparison circuits set to different reference voltages, and delays the output of the comparison circuit with the lower reference voltage for a predetermined period of time; a logic circuit that combines the output of the comparison circuit with a higher voltage with the output of the pulse stretcher and makes a logical judgment between the combined output and the output of the delay circuit;
In a fire detector that detects an abnormal state such as flame or heat, the alarm sound is made different depending on the type and degree of the abnormal state, and the lighting operation of an indicator light is made different in synchronization with the alarm sound. Features: Composite fire detector.