JPS6033035A - Light damping type smoke detector - Google Patents

Abstract

PURPOSE:To detect smoke having a prescribed concn. without being influenced by temp. dependency of a photodetector by connecting the prescribed two photodetectors to an arithmetic amplifier so that a signal corresponding to the difference of their photoelectric currents is impressed thereto. CONSTITUTION:The first photodetector 3 for detecting the light emitted from a light source 1 damped by the flowing-in smoke, and the second photodetector 6 for detecting the light emitted from the light source 1, transmitted through an optical path which is received no influence of the smoke are provided in a titled detector. These photodetectors 3, 6 are the elements formed on the same wafer and having uniform temp. characteristics, and are connected to a single arithmetic amplifier 7 so that the signal corresponding to the difference in their photoelectric currents is impressed thereto. The amplifier 7 generates an output when the input signal level attains a level corresponding to a prescribed sensitivity. Thus, the smoke having a prescribed concn. can be detected without being influenced by the temp. dependency of the photodetector.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a dimming type smoke detector that detects a fire by sensing attenuation of light from a light source by smoke flowing in at the time of a fire.

Conventionally, ionization type smoke detectors and scattered light type smoke detectors have been widely used as smoke detectors.

However, although ionization smoke detectors are sensitive to smoke generated at high temperatures such as ignition fires, they do not have sufficient detection characteristics for smoke generated from low temperature combustion such as smoldering fires. On the other hand, the scattered light type smoke detector has the disadvantage that although it operates sensitively for white smoke, it cannot obtain sufficient detection characteristics for black smoke.

On the other hand, dimming type smoke detectors that detect the dimming of light from a light source due to smoke detect any of the following: flaming fires, smoldering fires, fires with white smoke, and fires with black smoke. Detection characteristics uniformly correspond to smoke density, and it has the highest utility value as a smoke detector.

However, a drawback of dimming type smoke detectors is that unless the optical path length from the light source to the light receiving section is made long, it is not possible to obtain a light receiving output that exceeds the output change due to temperature change of the light receiving element.

Figure 1 is a graph showing the rate of change in the amount of received light (received light output) with respect to the optical path length based on the Lambert-Baer law, using the smoke concentration as a parameter, and Figure 2 shows the characteristics when the optical path length is short. ing.

For example, when trying to detect a fire at a smoke density of 20%/m, a change in light reception of about 1.11% is obtained with an optical path length of 5' crn. On the other hand, if a photodiode is used as a light-receiving element, the temperature dependence of the photodiode is usually 0°14 to 0.2%/°C, and the operating temperature range is 0°C to →- Absolute value of change rate of received light output at 50°C When referenced to 20'C, 10.14~0.2%/°C IX (±30°C) -4.2~
6%, and a temperature change in the installed state of the sensor causes a change that exceeds the rate of change in the amount of light received due to 20% smoke at 81 degrees Celsius. Therefore, in order to ignore the influence of temperature, it is necessary to ensure an optical path length of 25 cm or more from the graph of FIG.

Therefore, in the so-called spot-type dimming type smoke detector in which a conventional light source and a light receiving part are provided in the same housing, the light from the light source is reflected several times by a mirror and then incident on the light receiving part, for example, at a distance of 80 cm.
Although some devices have been designed to obtain an actual optical path length of
Regular ionization type and scattered light type smoke detectors have a mountain diameter of 5 or more.
Compared to the size of about 10 cm, it is too large to be used as a sensor, making it unsightly, and it is also expensive, so it can only be used for special purposes.

On the other hand, as shown in Utility Model Application No. 53-112'474M, two light-receiving elements are provided, one light-receiving element receives light from a light source that is attenuated by smoke, and the other light-receiving element receives light from a light source. There is also a dimming type smoke detector that detects fire from the difference in the received light output by directly inputting the light as a reference light, but the temperature dependence of the J: sea urchin phytodiode mentioned above is Since it is 0.14 to 0.2%/°C,
There is a maximum variation of 0°06%/°C in the elements, and considering the operating temperature range of 20 ± 30°C, 2.
1 due to a humidity change of ±30°C at a smoke density of 0%/111.
This will cause a change in the received light output of 8%, and in order to ignore this effect, the signal change amount ΔV b < small temperature change 1°8
% or more, that is, about △V=18%, it cannot be said that the sensor has good sensitivity, so the optical path length is about 8.
0 cm, and considering the variation in the characteristics of the amplifier installed for each light-receiving element, it is possible to obtain a human-sized dimming type smoke detector that is equivalent to conventional ionization type and scattered light type smoke detectors. was difficult.

The present invention was made in view of such conventional problems, and even if the size is equivalent to that of ionization type and scattered light type smoke detectors, the temperature dependence of the light receiving element is not affected by /i: +L. We offer dimming type smoke detectors that can detect smoke with a concentration according to the sensitivity setting.

The porpose is to do.

To achieve this objective, the present invention detects the light from the light source that is attenuated by the inflowing smoke (the first light receiving element detects the light from the light source that is attenuated by the inflowing smoke) and detects the light from the light source that is sent through an optical path that is not affected by the smoke. The first and second light receiving elements are elements having an optical semiconductor structure formed on the same unibar and having the same wet characteristics. The input of the element is connected to a single operational amplifier (op-amp) so that a signal corresponding to the difference in photocurrent between the two is applied.
The operational amplifier has a sensitivity setting means (which produces an output when the input signal level reaches a predetermined level according to the set sensitivity).
Off-celler 1~Adjustment circuit)

Embodiments of the present invention will be described below based on the drawings.

FIG. 3 is an explanatory diagram showing one embodiment of the present invention together with a sensor circuit.

First, the configuration of the optical system will be described. Reference numeral 1 denotes a light emitting diode that serves as a light source, and emits light toward a smoke detection area 2 formed inside the sensor housing into which smoke from the outside flows. A photodiode 3 serving as a first light-receiving element is installed at a position facing the light-emitting diode 1 through the smoke detection area 2, and an opening of a slit 4 installed on the incident side is connected to the photodiode 3. The light from the light emitting diode +'A-domain I that has passed through the smoke detection area 2 is made incident through the smoke detection area 2.

On the other hand, independently of the path of the light that enters the photodiode 3 from the light-emitting diode 1 through the smoke detection area 11!2, the light from the light-emitting diode 1 or I is transmitted through the slit 4 to a second light source by the optical fiber 5. A path for light entering the photodiode 6 as an element is provided. In addition, in such a dimming type optical system, the slit 4 is connected to the frame A1.
Since it is provided in close contact with the diode 33°6, the optical path is improved by the distance between the light emitting diode 1 and the slits 1 to 4.

A photodiode 3 into which the light from the light emitting diode 1 enters through the smoke detection area 2 and a photodiode 6 into which the light enters directly via the optical fiber 5 are connected in series with a common connection on the cathode side. The photodiodes 3.6 and 44 are arranged adjacently on the same unibar, and are formed on the same unibar. The temperature characteristics of the diodes 3.6 can be made almost the same.As an element in which the diodes 3.6) are formed adjacently on the same substrate, for example, 5P manufactured by Kodenshi Kogyo Co., Ltd. -2-29 etc. can be used, and the element itself is connected in anti-series with photodiodes 3.6 whose cathodes are commonly connected. It is possible to obtain a difference current of .

Two Fu II located adjacent to this same Univer
It has been experimentally confirmed that the relative output change due to the optical input of the diode 3.6 is 0.1±0.035% or less in the range of 0 to +50°C. Therefore, the amount of change in relative output of diodes 3 and 6 is 0.1 in the temperature range of -10 to +50°C, which is the working temperature of the smoke detector.
If it is within %, then in order to ignore this effect,
91 A sensor has good sensitivity if the signal change rate ΔV is 10 times or more than the temperature change of 1.0%, that is, Δv = i, o%, and the optical path length for ΔV = 1.0%. is the second
From the graph in the figure, it is approximately 5 cm.

Furthermore, since the light from the light emitting diode 1, which serves as the same light source, is incident on the photodiode A and the photodiode A, the relative current of the photodiode 3.6 obtained as a difference current can also be used against deterioration of the light source. The output does not change, and a stable relative output can be obtained even with temperature changes, and a similarly stable relative output can be obtained even with light source deterioration.

Next, the sensor circuit will be explained. The sensor circuit consists of a photodiode 3.
A differential circuit is electrically formed by the common connection on the cathode side of the A1-diode 3.6. The anode sides of diodes 3 and 6 are input connected to operational amplifier 7.
The anode side of the A-tie A-domain 6 is connected to the plus input terminal of the operational amplifier 7, and is connected to the minus side of the circuit.

In addition, the negative input terminal of the operational amplifier 7 is connected to the anode side of the diode 3, and the output is connected as a feedback via the feedback resistor R3. A circuit connection is made to apply a voltage proportional to 1 to the operational amplifier 7.

On the other hand, the operational amplifier 7 has a variable resistor V for offset adjustment.
R is provided, and a predetermined smoke density, for example, a light attenuation rate of 15%/m
By adjusting the variable resistor VR so that the output corresponding to the input voltage corresponding to the difference current between the photodiodes 3 and 6 that is jq due to the inflow of smoke becomes L level, Sensitivity settings can be made such that the operational amplifier 7 produces a 1-Rubel output no.j for smoke having a concentration exceeding 15%/■. Incidentally, in order for the operational j' amplifier 7 to operate as a comparator that produces an l-level output with the detection sensitivity set by the offset adjustment, the resistance value of the feedback resistor R3 should be made sufficiently large. Furthermore, when it is desired to increase the analog output according to the smoke density by 1q, by reducing the value of the feedback resistor R3, a detection output proportional to the difference current of the photodiode 3.6 can be obtained.

In this way, the sensor circuit of FIG. 3 has a circuit configuration in which the operational amplifier 111- is used to convert and amplify the difference current obtained by photoelectric conversion of the photodiodes 3 and 6, so that each filter Compared to the case where an operational amplifier is used for every 3.6 diodes of y+1-, it is possible to obtain an amplified output that depends only on the variation in the relative output of the photodiode 3.6 without causing variations in the characteristics between the 'A operational amplifiers. In addition, since the detection sensitivity is determined only by offset adjustment by H>f variable resistor V R, photodiodes 3 and 6 have λ
・1? This eliminates the need for mechanical adjustment of the optical system.

Next, when the optical path length B of the optical system is 1j, for example, the optical path length F]cm when the light attenuation rate is 20%/m shown in FIG. 2, the rate of change ΔV of the light receiving element is 1, 11 %, but the temperature change in the relative output of the two photodiodes 3.6 is only 0.1% in the range of -110 to +50°C.
Therefore, the signal change amount ΔV to ignore this temperature change ff10.1% is 10 times or more, for example, 1.0%, which satisfies the optical path length of 5 cm from the graph of FIG. Therefore, by shortening the optical path length, even if the rate of change ΔV is small, the effect of temperature can be ignored. Furthermore, by appropriately setting the amplification factor of the operational amplifier 7, the photocurrent of the foot diode 3 obtained by the inflow of smoke can be reduced. Slight changes can be detected with high precision. Therefore, according to the embodiment shown in FIG. 3, it is possible to realize a dimming type smoke sensor having an optical path length of -1Qcm or less and having the same size as conventional ionization type and scattered light type smoke detectors.

FIG. 4 shows another example of element connection in which two photodiodes are formed in the same shape used in the present invention. The anode sides of photodiodes 3 and 6 are commonly connected to obtain a differential output. Figure (b) shows a differential circuit in which photodiodes 3 and 6 are connected in parallel in opposite directions. The same figure (C) shows a differential circuit with a three-terminal structure in which the anode sides of photodiodes 3 and 6 are used as a common terminal, and the terminal sides of photodiodes 3 and 6 are taken out individually. , 6 can be obtained.

Fig. 5 shows an example of a specific circuit configuration of a dimming type smoke detector using the embodiment shown in Fig. 3. The constant voltage circuit 10 receives the power supply from the receiver (
A constant voltage is supplied to the instantaneous alarm circuit. Furthermore, since the example of actual color shown in FIG. 5 is taken as an example of the pulsed light emitting method of the light emitting diode 1, an oscillation circuit 11 is provided, and the output of the oscillation circuit 11 is connected to the C light emitting diode 1 through the resistor R4.
In addition, a natural source is intermittently supplied to the circuit section on the side of the operational amplifier 7 which operates as an amparator through a resistor R5 and an inductance L for cutting off high frequency components. As shown in the embodiment of FIG. 3, the light from the light emitting diode 1 is incident on the photodiode 3 via the detection area 2, and is also incident on the photodiode via another optical path formed by the optical fiber 5. The differential outputs of the photodiodes 3 and 6 are input to an operational amplifier 7, and the detection sensitivity is set by offset adjustment using a variable resistor VR provided in the operational amplifier 7. The output of the operational amplifier 7 is given to a two-stage amplifier circuit made up of transistors 13 and 14, and the collector of the transistor 14 is connected to the counter 12 via a resistor RIO. For example, a counter output is generated when the detection output of the operational amplifier 7 is obtained twice.

The counter output is used as a trigger signal to the gate 1- of the Lee resistor 15 connected between terminals 8 and 9 through the diode D1.
When the four Noiristers 15 are turned on, the caps 8 and 9, that is, the power signal line from the receiver, are short-circuited to a low impedance, and an alarm current is caused to flow. still,
Zener diode ZD connected in parallel to thyristor 15
and capacitor C1 are provided for surge voltage and noise absorption.

To briefly explain the operation of the embodiment shown in FIG. 5, the oscillation circuit 11 causes the light emitting diode 1 to emit light intermittently at regular intervals, and at the same time, the oscillation pulses of the oscillation circuit 11 cause the operation circuit 7 and its Transistor 1 installed in the output stage
3. Supply power to the amplifier circuit of 14 and light emitting diode 1
A pulse-like circuit operation is performed on the light-emitting frame. Therefore, the oscillation pulse width from the C1 oscillation circuit 11 should be set to 7C, which is sufficient for the circuit section including the A pen block 7 to be in a stable state after receiving the pulse signal via the resistor R5. ing. The light obtained by pulse driving of the light emitting diode 1 is incident on A1 to diode 3 via the smoke detection area, and at the same time is incident on the photodiode 6 via another optical path by the optical noibar.
A differential input corresponding to the difference between the photocurrents of 6 and 6 is given to the operational amplifier 7, and when there is no smoke flowing into the smoke detection area, the variable resistor VR
Due to the offset adjustment, the output of the operational amplifier 7 is at the L level, the transistors 9 and 10 are turned off, and the value of the counter 12 becomes zero.

On the other hand, if smoke flows into smoke detection area 2, 1, if smoke flows in, ! 7It-The light from light emitting diode 1 that enters diode 3 decreases, and the variable resistor VR
When the detection sensitivity set by off-cellar l-adjustment is obtained, for example, the light reception output due to smoke with a light attenuation rate of 15%/m is obtained, the operational amplifier 7 generates an H level output, and the transistor 13.14
When J:recounter 12 is turned on, the counter 12 is counted up. Subsequently, when the pulsed light of the next light emitting diode 1ζ1 similarly receives a light attenuation of 15%/m or more, the operational amplifier 7 similarly generates a level output of 1 to 1, and the i1 value of the counter 12 becomes When the set count of 2 is reached, the counter 12 generates an output to the gate of the thyristor 15, which triggers the thyristor 15 to short-circuit the power signal line from the receiver to low impedance, and receives the specified alarm current. Run it into the machine.

Next, the present invention will be described in detail. A first light receiving element detects light from a light source that is attenuated by inflowing smoke;
A second light-receiving element that detects light from a light source sent through an optical path unaffected by smoke is placed on the right, and this first and second
The light-receiving element is an element with an optical semiconductor structure formed on the same unibar and with uniform temperature characteristics, and the first d'3J:
and the second photodetector are input connected to a single arithmetic amplifier so that an I/A curve corresponding to the difference in photocurrent between the two is applied.
Since the 7i amplifier is equipped with a sensitivity setting means that generates an output when the input signal level reaches l≦a predetermined level according to the set sensitivity, the HM (I
Variations in the relative output with respect to h changes can be almost ignored, and even if the optical path length of the light source and photodetector installed through the smoke detection area is less than 10 cm, it depends on the temperature of the photodetector (2). It is possible to obtain a light receiving output according to the concentration of incoming smoke without being affected by the variation in smoke detectors.
It has become possible to put into practical use a dimming type smoke detector with a size of less than cm.

Furthermore, means for amplifying the differential output of the two light receiving elements ()
Since a single crushing amplifier is used, variations in characteristics between amplifiers can be ignored compared to the case where an amplifier is provided for each photodetector, and smoke can be reduced by shortening the optical path length. Even if the amount of change in the received light output with respect to the concentration is small, the amplifier's υ! It is possible to accurately detect the amount of light attenuation without being affected by variations in the light intensity.

Furthermore, since the detection sensitivity is set by adjusting the A-set of the crushing amplifier, there is no need for mechanical adjustment in the optical system where the attenuated light and the reference light are separately incident, making it possible to extremely easily adjust the detection sensitivity settings. You can easily do row 7J.

[Brief explanation of drawings]

Figure 1 is a graph showing the amount of change in light with respect to the optical path length of a dimming type smoke detector using smoke concentration as a parameter, and Figure 2 is a graph showing the short portion of Figure 1 with a short optical path length. 3 is an explanatory diagram showing one embodiment of the present invention, FIG. 4 is a circuit diagram showing another embodiment of differential connection of two photodiodes used in the present invention, and FIG. 3 is a circuit diagram showing a specific embodiment of a dimming type smoke detector using the embodiment of FIG. 3. FIG. 1: Light emitting diode (light source) 2: Smoke detection area 3: Photodiode (first light receiving element) 4 Nislit 5: Optical fiber 6: Photodiode (second light receiving element) 7: Operational amplifier 8.9 = terminal 10: Constant Voltage circuit 11: Oscillation circuit 12: Counter 13.14: L-Ran resistor 15: Suiristar Patent applicant Hochiki Co., Ltd. Agent Susumu Takeuchi 1 Figure L E & Length (cm)

Claims (1)

[Claims] In a dimming type smoke detector that detects that the light from the light source is attenuated by the light receiving part due to smoke flowing in during a fire and outputs a fire signal, A first light-receiving element for detecting light and a second light-receiving element for detecting light sent from a light source through an optical path unaffected by smoke are arranged on the right, and the first and second light-receiving elements are located on the same uniform bar. The first light-receiving element and the second light-receiving element are input-connected to an operational amplifier so as to apply a signal according to the difference current between the two, and the first light-receiving element and the second light-receiving element are connected as inputs to an operational amplifier so as to apply a signal according to a difference current between the two light-receiving elements. Features: 1- Dimming type smoke detector.