JPS6044720B2 - Transparent smoke detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a transmission type smoke sensor that detects smoke by detecting a decrease in the amount of transmitted light using a light receiving element.

Transmissive smoke detectors detect a decrease in the output of the light receiving element caused by smoke intervening on the optical axis between the light source and the light receiving element, and output this as a fire signal.
However, the output of the light-receiving element described above decreases due to factors other than smoke caused by a fire, such as misalignment of the optical axis between the light source and the light-receiving element due to some rhythm, or the invasion of insects, etc. The major drawback was that it frequently issued false alarms.

This invention was made in view of the above points, and its purpose is to eliminate the above-mentioned misinformation,
Transparent type that distinguishes and outputs whether the sensing output is caused by fire smoke, that is, a fire factor, or a factor other than fire smoke, that is, a non-fire factor. The purpose is to provide smoke detectors.

This invention provides a transmission type smoke detector that detects smoke by detecting a decrease in the amount of transmitted light with a light receiving element, and when a change in the output of the light receiving element is due to the smoke that is a cause of a fire, a gradual change is detected. This method detects temporal changes in the output of the light-receiving element by focusing on the fact that when the above-mentioned non-fire factors such as insects cause a sudden change, the output of the light-receiving element changes over time. This is a transmission-type smoke detector that is provided with an identification circuit that identifies temporal changes in output, and configured to output a fire signal and a non-fire signal in a manner that discriminates and outputs a fire signal and a non-fire signal based on the output of this identification circuit. Hereinafter, detailed examples thereof will be described based on the drawings. FIG. 1 shows an embodiment of the above-mentioned transmission type smoke detector, in which the identification circuit sets a threshold h1 to detect a decrease in the output level of the light receiving element 1 when smoke is detected.
a second level discriminator 3 that detects that the output of the light receiving element 1 has decreased below a second threshold Vh2 that can be set even lower than the threshold h1; comprising a logic circuit 4 that operates based on the logical product of the detection output of the first level discriminator 2 and the non-detection output of the second level discriminator 3, the operation output of the logic circuit 4 being used as a fire signal; Further, the output of the second discriminator 3 is configured to be outputted as a non-fire signal.

Here, the light receiving element 1 is located in the smoke introduction space. (Illustration omitted)
It is a photoelectric conversion element that converts the light 1 from the light source 5 that has passed through the light source 5 into an electrical signal, and the converted output is amplified by the preamplifier 6 and then transmitted to the above-mentioned. 1, and are input to second level discriminators 2 and 3, respectively. The detection output of the first level discriminator 2 passes through the delay circuit 7 and then enters the positive logic input of the logic circuit 4, and the detection output of the second level discriminator 3 enters the RS flip-flop 58. A set input S is input, and a set output Q of this RS flip-flop 8 is input to a negative logic input of the logic circuit 4.
each connected. This RS flip-flop 8
The reset input R is connected to a reset switch 9. The AND output of the logic circuit 4 is connected as a fire signal, and the set output Q of the flip-flop 8 is output as a non-fire signal. 2a and 2b each illustrate the operation of the transmission type smoke detector shown in FIG. 1. FIG.

Figure 2a shows points A-G when smoke from a fire is detected.
In this case, the concentration of smoke gradually increases, and the output of the light receiving element 1 gradually decreases as the fire breaks out, as shown in A of the figure, and the setting of the first level discriminator 2 changes. It becomes below the threshold value Vhl. And this threshold h1,
It comes to float between the second cutoff value Vh2 set lower than this. At this time, the first level discriminator 2 starts to emit a detection output from the time when the output of the light receiving element 1 falls below the first threshold value Vhl, as shown in FIG. On the other hand, since the output of the light receiving element 1 does not fall below the second threshold value V, the second level discriminator 3 issues a detection output as shown in FIG. Therefore, the RS flip-flop 8
is not set. By passing through the delay circuit 7, the detection output from the first level discriminator 2 is delayed by a slight delay time Td, as shown in FIG. enter.

As a result, the positive logic input of the logic circuit 4 becomes active, and the set output of the BS flip-flop 8 does not appear on the negative logic input as well, as shown in FIG. , it becomes active after all. As a result, the logic circuit 4 outputs the AND output as a fire signal, as shown in FIG.
As for the non-fire signal, since the RS flip-flop 8 is not set, it is not output as shown in FIG. Figure 2b shows the operation at each point A to G when a factor other than a fire occurs, such as an insect flying into the smoke introduction space. In this case, the output of the light receiving element 1 is as shown in Figure A. Then, it rapidly decreases from the steady value to below the second threshold value Vh2 to near the lowest value, and then fluctuates so as to increase again. In other words, instead of taking an intermediate value like when smoke is introduced, the temperature rapidly changes between the extremes of a steady value or a minimum value. Therefore, the first level discriminator 2 outputs a detection output as shown in B in the figure, and the second level discriminator 3 outputs a detection output as shown in C in the figure.
Each is output. By passing through the delay circuit 7, the detection output of the first level discriminator 2 is delayed by a slight delay time Td, as shown in FIG.
enters the positive logic input of Further, the second level discriminator 3
The detection output of the RS flip-flop 8 enters the set input of the RS flip-flop 8, and the set output of the RS flip-flop 8 is input to the negative logic circuit 4 of the logic circuit 4, as shown in FIG. You will be able to enter the physical input. As a result, the positive logic input of the logic circuit 4 becomes active, but the negative logic input is connected to the output of the RS flip-flop 8, as shown in FIG. , becomes inactive. As a result,
The logic circuit 74 does not output a fire signal as shown in Figure F, and the set output Q of the S flip-flop 8 outputs a non-fire signal as shown in Figure G. become. This non-fire signal continues to be emitted until the reset switch 9 is operated. Here, the delay circuit 7 is for compensating for the delay in the operation of the RS flip-flop 8, and thereby the logic circuit 4
It is also possible to eliminate the time lag between the two human input signals. FIG. 3 shows another embodiment of the transmission type smoke sensor and detector according to the present invention, in which the identification circuit has a first detection circuit that detects a decrease in the output level of the light receiving element 1 when smoke is detected. Level detector 2
and a differentiation circuit 10 that detects the rate of change in the output level of the light receiving element 1, and a differentiation output of this differentiation circuit 10 is set to a set value V.
A second level discriminator 1 detects that the level has become h3 or higher.
1, the detection output of the first level discriminator 2, and the second level discriminator 2.
and a logic circuit 4 that operates based on the AND of the non-detection outputs of the level discriminator 11, the operating output of the logic circuit 4 is used as a fire signal, and the detection output of the second level discriminator 11 is used as a non-fire signal. They are configured to be output as signals, respectively.

Other detailed components are the same as those shown in FIG. 1 above, so common symbols are given and detailed explanations are omitted. 4a and 4b each illustrate the operation of the transmission type smoke detector shown in FIG. 3. FIG.

Figure a shows points A and H- when smoke from a fire is detected.
With operation at N, in this case the concentration of smoke gradually increases,
As shown in FIG. 1A, the output of the light receiving element 1 draws a gentle curve as a fire occurs, and becomes lower than the threshold value Vhl set for smoke detection. At this time, the differential output of the differentiating circuit 10 hardly appears as shown in H in the figure because the light receiving element 1 changes slowly.
On the other hand, the detection output of the first level detector 2 appears as shown in FIG. 1 because the output of the light-receiving element 1 becomes below the threshold h1, and passes through the delay circuit 7 to K in the same figure. As shown, it enters the positive logic input of the logic circuit 4. The detection output of the second level detection 11 is output from the differentiation circuit 10.
It is found that the differential output of 1 is almost non-existent, but does not appear as shown in FIG. The set output that should be entered into the output is not issued, as shown in Figure L. As a result,
Both the positive logic input and the negative logic input of the logic circuit 4 become active, and the logical product output is outputted as a fire signal, as shown in FIG. As for the non-fire signal, since the RS flip-flop 8 is not set, it is not output as shown in FIG. 4th b
The figure shows the operation at each point A, E-N when a factor other than a fire occurs, such as an insect flying into the smoke introduction space. In this case, the output of the light receiving element 1 is as shown in figure A. ,
Change rapidly.

Therefore, as shown in FIG. Such detection outputs are output respectively. When the differentiated output of the differentiating circuit 10 exceeds the set value Vh3, the second level discriminator 11 generates a detection output as shown in J of the same figure, and the RS flip-flop 8 is set. The detection output of the first level discriminator 2 passes through a delay circuit 7 and enters the positive logic input of the logic circuit 4, as shown in FIG. Further, the set output Q of the S7 flip-flop 8 set by the detection output of the second level discriminator 11 also enters the negative logic input of the logic circuit 4, as shown in FIG. As a result, the positive logic input becomes active, but the negative logic input becomes inactive, and the AND output is not output as shown in FIG. 9M. In other words, no fire signal is output. At this time, since the RS flip-flop 8 is set by the second level discriminator 11, its set output Q can continue to be emitted as a non-fire signal until the reset switch 9 is operated. In the above, it has been shown that fire signals and non-fire signals are output differentially in each of the embodiments. It is shown in FIG.

The circuit shown in the figure connects the smoke alarm side, that is, the transmitting side, and the monitoring side, that is, the receiving side, as in the conventional case, using two electric wires.
It is designed so that it can be tied with only 1 and 12. According to the figure, on the transmitting side, two semiconductor current control devices (hereinafter referred to as SCRs) are connected between two wires that also serve as power supply lines.
It is abbreviated as. ) 12 and 13 are inserted in parallel. One SCR12 is connected so as to be triggered by a fire signal, and the other SCR13 is connected so as to be triggered by a non-fire signal, and the current flowing when the conduction is conducted is suppressed to a constant rate. An impedance R1 is inserted in series. The receiving side, which is connected to the transmitting side via the electric wires 11 and 12, connects the break contact switch trap, the drive coil of the first relay R1, and the light emitting side element 14a of the photo coupler 14 to the electric wires 11 and 12, respectively. The power supply 15 is connected in series, and the drive coil of the second relay R2 is connected to the break contact switch trap and the first relay.
The break contact Rlb of the relay R1 and the light-receiving element 14b of the photo coupler 14 are connected to the power source 15 in series. and,
Pilot lamp L1 and buzzer BZ to notify of fire
However, a non-fire alarm is also notified via the make contact Rla of the first relay R1! The pilot lamps are connected to the power source 15 through the make contact R2a of the second relay R2. The operation of the circuit configured in this way is as follows. First of all,
A fire signal is issued on the calling side, and one SCRl2:
Once it is triggered and becomes conductive, the power supply 1 on the receiving side
From 5, break contact switch? , the drive coil of the first relay R1, and the light emitting side element 14a of the photo coupler 14.
A current path is formed through the electric wires 11, 12 and SCRl2, and as a result, the first relay R1 is activated, the make contact of this relay R1 is closed, the pilot lamp plate that notifies the fire is lit, and the buzzer is activated. BZ is activated and starts emitting an alarm sound. Next, when a non-fire signal is issued on the transmitting side and the other SCR13 is triggered to become conductive, the power source 15 on the receiving side is connected to the break contact BS1, the drive coil of the first relay R1, and the photocoupler. -14 light emitting element side 14a1 electric wires 11, 12
, a first current path flowing through impedance R1 and SCRl3 is formed. However, the current flowing through SCRl3 at this time is suppressed to a constant rate or less by impedance R1 inserted in series with SCRl3.
Sufficient drive current to operate the relay R1 does not flow through the drive coil of the ninth first relay R1, and therefore, no drive current is supplied to the pilot lamp L1 and the buzzer Wl2, causing a fire alarm. is not carried out either. However, even if sufficient current does not flow to operate the first relay R1, this current can sufficiently operate the light emitting side element 14a of the photo coupler 14, so that the light receiving element 14a of the photo coupler 14 can be operated sufficiently. The element 14b is driven to a conductive state using light as a medium. For this reason, the above power supply 1J5
A second current path is formed through the break contact switch trap, the break contact Rlbl of the first relay R1, the drive coil of the second relay R2, and the light receiving element 14b of the photo coupler 14, and this second current Only the second relay R2 is actuated by the current flowing through the path,
The make contact Rla closes, and the pilot lamp L2, which indicates a non-fire situation, comes on. and an SCR that has become conductive due to a fire signal or non-fire signal.
Is l2 or 13 the break contact switch on the receiving side? By manually operating , it is possible to return to the state before the conduction state. As described above, the present invention provides a transmission-type smoke detector that detects smoke by detecting a decrease in the amount of transmitted light with a light-receiving element, and is provided with a circuit that identifies temporal changes in the output of the light-receiving element. This is a transmission type smoke detector configured to discriminately output a fire signal based on the output of the sensor.By being configured in this way, it is possible to determine whether the detected output is caused by smoke from a fire. Alternatively, it is now possible to distinguish and output whether the smoke is caused by a factor other than fire smoke, thereby eliminating false alarms and significantly increasing the reliability of the detector.

[Brief explanation of drawings]

FIG. 1 is a block diagram showing an embodiment of a transmission type smoke detector according to the present invention, FIGS. 2a and 2b are waveform diagrams for explaining the operation of each part of the sensor shown in FIG.
Figure 3 is a block diagram showing an embodiment, Figures 4a and 4.
FIG. b is a waveform diagram for explaining the operation of each part of the sensor shown in FIG. 3, and FIG. 5 is a circuit diagram showing a connection example of the sensor shown in FIG. 1 or 3. 1... Light receiving element, 2, 3, 11... Lebel discriminator, 4... Logic circuit, ゛5... Light source,
8...RS flip-flop, 10...
・Differential circuit.

Claims (1)

[Scope of Claims] 1. In a transmission type smoke detector that detects a decrease in the amount of transmitted light using a light receiving element, and uses an identification circuit to identify a temporal change in the detection output to notify a fire, the identification circuit detects smoke. a first level discriminator having a threshold set to detect a decrease in the output level of the light receiving element when detected; a delay circuit that delays the detection output of the first level discriminator for a certain period of time; a second level discriminator that detects that the output of the output has decreased below a second threshold value that can be set even lower than the threshold value; a logic circuit that operates by logical product, and uses the operating output of the logic circuit as a fire signal;
Further, a transmission type smoke detector characterized in that the output of the second discriminator is outputted as a non-fire signal. 2. In the transmission type smoke detector according to claim 1, the identification circuit includes a first level discriminator that detects a decrease in the output level of the light receiving element when smoke is detected;
a delay circuit that delays the detection output of the level discriminator for a certain period of time; a differentiation circuit that detects the rate of change in the output level of the light receiving element; and a second differentiation circuit that detects when the differential output of the differentiation circuit exceeds a set value. a level discriminator, and a logic circuit that operates based on the AND of the delayed output of the delay circuit and the non-detection output of the second level discriminator, and uses the operation output of the logic circuit as a fire signal, and A transmission type smoke detector characterized in that the detection output of the second level discriminator is a non-fire signal, and is outputted respectively.