JPS62272138A - Dimming type smoke detector - Google Patents

Abstract

PURPOSE:To make a smoke detection space substantially long by driving a light emitting device plural times in an arithmetic period based on a photodetection output to emit light, and integrating the quantity of attenuation of a photodetection output due to smoke and outputting a smoke detection signal and a fire detection signal. CONSTITUTION:Light from the light emitting device 10 of a light emission driving part 1 is sent to the light receiving device 20 of a light reception part 2 through the smoke detection space 15. The light receiving device 20 generates a light reception current and a driving signal is inputted to an operational amplifier 30 by capacitors C1 and C2 and switches S1-S4 of the circuit of the light reception part 2 and the switching driving circuit 60 of an arithmetic control part 50 to drive the light emitting device 10 set times in the arithmetic period. Then when the light is attenuated in the smoke detection space 15 owing to smoke, the quantity of light attenuation is integrated by the operational amplifier 24 by set times. The integration output is inputted to a smoke quantity arithmetic part 64 and a fire level detecting circuit 66 and compared with their threshold levels to output the smoke detection signal or fire detection signal. Thus, the light emitting device is driven by plural times to integrate the quantity of light attenuation, so the effective length of the smoke detection space is made long and the detector is reduced in size.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention (Field of Industrial Application) The present invention provides a light emitting part and a light receiving part facing each other with a predetermined smoke detection space in between. The present invention relates to a dimming type smoke detector in which a light receiving section receives attenuated light due to smoke and detects a fire based on the light receiving output of the light receiving section.

(Prior art) In a conventional integrated type attenuation smoke detector, a light emitting part that emits light and a light receiving part that receives light emitted from the light emitting part face each other with a predetermined smoke detection space in between. When smoke enters the smoke detection space, the light emitted from the light emitting part is attenuated by the smoke, and fire detection is performed based on the attenuated light receiving output of the light receiving part. In order to obtain an optical path length between The detection sensitivity was increased by increasing the amount of attenuation caused by smoke.

(Problems to be Solved by the Invention) However, in such a dimming type smoke detector, the emitted light is attenuated each time the emitted light from the light emitting part is reflected by the mirror, and the mirror becomes dirty due to aging. Furthermore, not only does the attenuation rate increase, but the optical adjustment mechanism using the mirror becomes complicated, leading to an increase in cost.

For this reason, the inventors provided a light receiving section facing each of the plurality of light emitting sections, and the light emitted from each light emitting section was incident on the corresponding light receiving section, and the light was attenuated by smoke from each light receiving section. The integrated means integrates the smoke detection signals obtained and calculates the amount of smoke, thereby providing the same function as if the distance between the light emitting part and the light receiving part, that is, the smoke detection space, was set substantially wider, and at the same time reducing costs. proposed a dimming type smoke detector (patent application 1983-
No. 85605).

By the way, such a dimming type smoke detector requires a plurality of light emitting parts and the same number of light receiving parts as the light emitting parts. It has been desired to further reduce the size of dimming type smoke detectors.

(Means for Solving the Problems) The present invention has been made in view of the above-mentioned problems, and is designed to increase the length of the optical path between the light emitting part and the light receiving part within a limited housing so as to substantially create a smoke detection space. While having the same functionality as when set for a long time,
The object of the present invention is to significantly reduce costs and provide an integrated dimming type smoke detector that is further miniaturized.

In order to achieve this object, the present invention provides a dimming type smoke detector in which a pair of light emitting device and light receiving device are provided facing each other.
A driving means is provided to drive the emitter multiple times based on the light reception output from the light receiver within the calculation cycle, and smoke is detected based on the light reception output that is the cumulative amount of attenuation of light due to smoke from the light receiver in each calculation cycle. A fire level detection means is provided which outputs a signal and further compares the received light output obtained each time the light emitter is driven with a predetermined threshold level and outputs a fire detection signal when the light reception output falls below the threshold level.

(Function) The function of the present invention with such a configuration is that first, the driving means drives the light emitter to emit light multiple times based on the received light output within the calculation cycle, and by repeating this light emitting drive, the amount of attenuation of light due to smoke is reduced. By obtaining the accumulated received light output, it is possible to obtain a level change in the received light output due to smoke that is essentially the same as detecting smoke at a distance equal to the installation distance of the emitter and receiver multiplied by the number of times the light is emitted. Even if the installation interval between the emitter and receiver is short, a sufficiently large change in the received light output can be obtained due to the attenuation of light due to smoke.

Furthermore, if the light reception output falls below the threshold level before the calculation cycle in which the light reception output is obtained by accumulating the amount of light attenuation due to smoke due to repeated light emission driving, it is immediately determined that there is a fire, and a fire detection signal is sent. When the smoke concentration is high, a fire can be detected immediately without the delay time caused by repeated light emission driving.

(Embodiment) FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

First, to explain the configuration, 1 is a light emitting drive section, and 2 is a light receiving section. First, on the light emitting drive section 1 side, an operational amplifier 30 is provided which feeds back the light reception output transferred by the switching control of the light receiving section 2 side.The feedback output from the operational amplifier 30 is input to the non-inverting input terminal of the operational amplifier 9. The output of the operational amplifier 9 is connected to a transistor Q1 for driving light emission via a resistor R1.
given on the basis of. A light emitter 10 is connected to the collector side of transistor Q1, and a resistor R2 for overcurrent prevention is connected to the emitter side. The light from the emitter 10 is given to the receiver 11 via the optical fiber 16.
The feedback voltage obtained by passing the light receiving current of the light receiver 11 through the resistor R3 is applied to the inverting input terminal of the operational amplifier 9, and while the light emitter 10 is compensated for dirt and temperature, the luminance of the light emitter 100 is controlled by the operational amplifier. The amount of light emitted is controlled in accordance with the level of feedback light received from 30.

A smoke detection space 15 is provided at a predetermined distance from the light emitter 10.
The light receivers 20 of the light receiving unit 2 are arranged opposite to each other via the
The smoke detection distance is set to, for example, about 10 cm. The light receiver 20 has a light receiving level record that is charged by the light receiving current.
A first capacitor C1 as a storage means is connected in series,
The capacitor C1 is charged with a light receiving voltage corresponding to the light attenuated by the smoke flowing into the smoke detection space 15. The charging voltage of the first capacitor C1 is connected to the non-inverting input terminal of the operational amplifier 22, and this non-inverting input terminal is connected to the reference voltage voltage V r via the analog switch S1 using an FET.
It is connected to the application terminal of ef, and is also connected to ground via an analog switch S2 and a resistor R7.

The output of the operational amplifier 22 is connected to a diode D2 for backflow prevention.
, an analog switch S3 and a resistor R8 to a non-inverting input terminal of an output operational amplifier 24, and the operational amplifier 24 operates as a buffer amplifier by connecting its output end to the inverting input terminal. Further, a second capacitor C2 is connected between the output side of the resistor R8 and the ground as a storage means for the received light output, and the second capacitor C2 is charged and held in the first capacitor C1 under the control of the analog switch S3. The received light voltage is transferred and charged.

The charging voltage of the capacitor C2 is feedback-connected to the non-inverting input terminal of the operational amplifier 30 on the light-emitting driver 1 side via the analog switch S4, and a resistor R10 is connected between this non-inverting input terminal and ground. Therefore, when the analog switch S4 is turned on, the charge in the second capacitor C2 is discharged through the resistor R10, so that the terminal voltage of this resistor R10 becomes the feedback voltage.

The first and second capacitors C1 and C2 and the analog switches 81 to S4 on the light receiving section 2 side constitute a switching delay means that delays the light receiving output by a certain period of time under switching control and returns it to the light emitting side. .

The control of the analog switches 81 to S4 for delaying the received light output by switching control and returning it to the light emitting side is performed using switching signals 01 to e4 from the switching drive circuit 60 that operate based on clock pulses from the clock pulse generator 62. For example, the switching signals 01 to e4 are as shown in the timing chart of FIG.

In FIG. 2, first, in the first cycle T1, the light emitter 10 is not driven to emit light, and the capacitor C1 connected in series with the light receiver 20 is not charged with the light receiving voltage. At this point, the analog switches S1 and S3 are turned on simultaneously, and the second capacitor C2 is charged with the reference voltage yrer via the operational amplifier 22. At this time, the first capacitor C1 is also connected to the reference voltage V at the same time.
Since the first capacitor C1 is charged to ref, the analog switch S2 is turned on at the next time t12, and the first capacitor C1 is discharged and reset.

Subsequently, at time t13, the analog switch S4 is turned on, and the MQ voltage Vrcf charged in the capacitor C2 is fed back (differentially input) to the operational amplifier 30 on the light receiving side. 10 performs the first light emission drive. Therefore, the light emitter 1 at time t13
With the light emission drive of
A received light voltage is charged according to the intensity of the light that has been attenuated by the smoke that has flowed into the device.

When the switching control of the T1 cycle is completed, the analog switch S3 is turned on at time t21 of the next T2 cycle, and the light reception voltage held in the capacitor C1 is transferred and charged to the capacitor C2. Note that at time t21, since the light receiving voltage is 1q applied to the capacitor C1, the analog switch S1 is turned off. Subsequently, at time t22, the analog switch S2 is turned on to discharge and reset the light receiving voltage of the capacitor C1 via the resistor R7, and at the next time t23, the analog switch S4 is turned on again, and the charged light is transferred to the capacitor (J C2). The voltage is fed back to the operational amplifier 30, and the light emitter 10 is driven to emit light for the second time.

Hereinafter, the switching control in which the analog switches 33, 32 and S4 are sequentially turned on is repeated in the same manner for cycles T3 to Tn, and the light emission drive is performed N times by feedback of the light reception output within a predetermined calculation cycle Ta in which the analog switch S1 is turned on next. repeat.

Here, if there is no smoke flowing into the smoke detection space 15, the light reception output from the operational amplifier 24 will remain at the reference voltage V ref even if the light emission drive is repeated N times. When smoke inflows, the first light is attenuated by the smoke in the smoke detection space 15 by repeating the light emission drive N times by the light emission drive by feedback of the light reception output, and the amount of light attenuation due to the smoke is reduced by repeating the light emission drive N times. The accumulated received light output is transmitted to the operational amplifier 24.
You will be able to get it from

The N driving periods consisting of the T1 to Tn cycles are determined within the calculation period Ta, and when the switching control of the 1 to Tn cycles is completed, the process returns to the T1 cycle again.
Switching control is repeated in the same way.

Referring again to FIG. 1, reference numeral 50 denotes an arithmetic control section, which calculates the amount of smoke and detects a fire based on the light received from the light receiving section 2 by driving the light emitting drive section 1 to emit light.

That is, the calculation control section 50 includes a switching drive circuit 60.
are provided, and analog switches 81 to S4 on the light receiving section 2 side are provided.
As shown in the timing chart of FIG. 2, switching signals 01 to e4 for controlling switching are generated based on clock pulses from a clock pulse generator 62.

Also, the calculation cycle determined by the switching cycles T1 to Tn of the switching drive circuit 60! The number of times Nn of light emission driving within 1llTa is set by the number of light emission setting circuit 65, for example, Nn=
It is set to 10 times.

On the other hand, 64 is a smoke amount calculating section, which receives the light receiving output obtained from the operational amplifier 24 of the light receiving section 2 obtained every calculation period Ta, which is the accumulated amount of attenuation of light due to smoke by repeating the light emission drive N0 times. The amount of smoke is calculated based on the signal level of the received light output, and the smoke amount detection signal is given to the output circuit 68 and converted into, for example, a current signal (4 to 20 mA), a voltage signal (1 to 5 V), or digital data. It is sent to a fire receiver such as a monitoring center (not shown).

Here, the calculation of the smoke amount by the smoke amount calculation unit 64 is based on the relationship between the received light level [) Based on this experimental result, a conversion table between the received light level [)
) Converts X into a smoke amount and sends a smoke amount detection signal to the output circuit 68.

In this embodiment, the smoke amount calculating section 64 converts the light reception signal level from the light receiving section 2 into a smoke amount and outputs it.
The smoke amount calculating section 64 may directly output the received light signal level without converting it into smoke (2).

Further, the arithmetic control section 50 includes a fire level detection circuit 66 into which the light receiving output from the light receiving section 2 is input. A predetermined threshold level for determining a fire is set in the fire level detection circuit 66, and the light reception output of the light receiving section 2 is compared with the threshold level, and when the light reception output falls below the threshold level, a fire detection signal is output. It is output to the output circuit 68. That is, the fire level detection circuit 66 is provided independently of the smoke amount calculation process for each calculation period Ta in the smoke amount calculation section 64, and the light reception output due to light emission drive is below the threshold level regardless of the calculation period Ta. If it goes down, it is immediately determined that there is a fire and a fire detection signal is output.

Receives the fire detection signal from this fire level detection circuit 66 (
The output circuit 68 sends a current signal, a voltage signal, or a digital signal indicating that there is a fire to the fire receiver on the center side, regardless of the output of the smoke amount calculating section 64.

Next, the operations of the smoke amount calculation section 64 and the fire level detection circuit 66 provided in the calculation control section will be explained.

In a normal monitoring state, every calculation cycle Ta, the smoke amount calculation unit 64 converts the received light level [) The amount of smoke is determined using a table, and the output circuit 68 transmits a detection signal indicating the amount of smoke to a fire receiver at the center, and the center side displays the amount of smoke and processes to determine whether or not there is a fire. If smoke from a fire enters the system, it will be determined that there is a fire when a predetermined amount of smoke is detected.

On the other hand, the fire level detection circuit 66 compares the light reception output obtained each time the light emission is driven with a threshold level. When the received light output, which is the accumulation of light attenuation due to smoke, decreases significantly and falls below the threshold level, a fire detection signal is given to the output circuit 68, and a fire detection signal is sent to the fire receiver on the center side. send it out,
A fire alarm can now be issued immediately without the center having to judge the amount of smoke.

(Effects of the Invention) As described above, according to the present invention, the light emitter is driven to emit light multiple times based on the light reception output from the light receiver within the calculation cycle, and the smoke from the light receiver is driven to emit light in each calculation cycle. A smoke detection signal is output based on the light reception output in which the amount of light attenuation is accumulated, and the light reception output obtained for each light emission drive is compared with a predetermined threshold level, and a fire detection signal is generated when the light reception output falls below the threshold level. , the change in light reception output equivalent to setting the effective length of the smoke detection space longer is
q, the dimming type smoke detector can be significantly miniaturized, and the cost of the dimming type smoke detector can be reduced.

Additionally, the sensor side judges whether there is a fire or not by comparing the light reception output obtained each time the light is driven with a threshold level, so if a high concentration of smoke flows in, there will be a delay time due to the light being driven multiple times. Furthermore, since the sensor side detects the fire, it is possible to reduce the processing burden on the center side, which judges the fire based on the smoke amount detection signal from the sensor.

On the other hand, as a delay means when returning the light receiving output to the light emitting side, a predetermined delay time is obtained by transfer charging of a capacitor using switching control, which prevents transmission distortion when using a delay line or delay element. It is possible to accurately feed back the light reception signal and repeat the light emission drive.

[Brief explanation of the drawing]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, and FIG. 2 is a timing chart of switching signals for driving the light emission a plurality of times as shown in FIG. 1: Light emission driving section 2: Light receiving section 9.22, 24, 30: Operational amplifier 10: Light emitter 1'l, 20: Light receiver Ql: Transistor R1, R2, R3, R7, R8, R10: Resistor C1, C
2: Capacitor 31. S2. S3. S4: Analog switch 50: Arithmetic control unit 60 Niswitching drive circuit 62: Kurotsuta pulse generator 64: Smoke amount calculation unit 65: Number of light emission setting circuit 66 Fire level detection circuit 68: Output circuit

Claims (1)

[Scope of claims] In a dimming smoke detector including a pair of light emitters and a light receiver facing each other, the light emitter is driven a plurality of times based on the received light output from the light receiver within a calculation cycle. means, an output means for outputting a smoke detection signal based on a received light output in which the amount of attenuation of light attenuated by smoke from the light receiver is accumulated for each calculation cycle, and each time the light emitter is driven by the drive means. 1. A dimming type smoke detector comprising fire level detection means for comparing the received light output obtained in the above with a predetermined threshold level and outputting a fire detection signal when the received light output falls below the threshold level.