JPS5834555Y2 - Storage type fire detector - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a storage type fire sensor in which a fire detection signal level determination circuit has hysteresis characteristics.

Conventionally, in order to prevent non-fire alarms and improve the reliability of fire signals, so-called storage-type fire detectors have been used that issue a fire alarm only when a fire detection signal exceeding a predetermined level is obtained for a certain period of time. It is used.

However, while storage type fire detectors have a low number of non-fire alarms, they have the following drawbacks.

In other words, as is known from various fire experiments, it is known that fires that generate a large amount of smoke or changes in smoke concentration near the ignition point generally change significantly as shown in Figure 1. Despite these rapid changes, the average smoke density continues to increase over time.

In response to such changes in smoke concentration over time, in conventional storage type fire detectors, if smoke has a level determination operating point at a certain level, for example, at a smoke density of 1 OVWL, the sensor will stop when this operating point concentration is reached. starts the accumulation operation and issues a fire alarm output when the concentration exceeding the operating point continues for a certain period of time, for example 30 seconds or more.

Therefore, even if 10%/m2 is temporarily reduced due to cigarette smoke, etc.
Even if the smoke concentration reaches the above level, it will diffuse after a certain period of time within the accumulation time and the concentration will become extremely low.
This avoids situations in which a non-fire signal is emitted.

However, as is clear with reference to Figure 1, even in actual fires, a situation in which the rate temporarily exceeds 10%/m often occurs in the early stages of the fire, and the detector starts accumulating operation each time, but immediately Since the concentration becomes low, the operation of resetting the accumulation operation is repeated.

In this way, regardless of the spread of the fire, the sensor repeatedly resets the storage operation that has been started, ultimately leading to a delay in the power generation of the fire.

Now, in FIG. 1, if Δt=t12-t1□ is the time required to complete the accumulation operation, the time to issue the fire signal will be after t15 for curve a,
Conventional storage type fire detectors have the disadvantage of not being able to detect fires early.

The purpose of this invention is to enable early detection of fires by providing the level determination circuit with a hysteresis characteristic that makes the determination level of the fire detection signal that starts the accumulation operation different from the determination level of the fire detection signal that resets the accumulation operation. The present invention provides a storage type fire detector that

Embodiments of this invention will be described below with reference to the drawings.

FIG. 2 is a block diagram showing the basic circuit configuration of the storage type fire detector according to this invention, in which a detection section 10 detects physical changes in the surroundings due to a fire, and an output signal from the detection section 10 reaches a predetermined level. A level determination circuit 12 having a hysteresis characteristic that generates an output signal when the level exceeds the level;
It consists of an accumulation circuit 14 that accumulates the output of the fire detection signal for a predetermined period of time and activates an alarm circuit 16 to send a fire alarm to the receiver.Since the level judgment circuit 12 has hysteresis characteristics, it is difficult to accumulate the fire detection signal. The operation level for starting the storage operation is higher than the recovery level for resetting the storage operation.

Figure 3 shows the operating level N2 and recovery level N1 of the level judgment circuit with respect to changes in smoke density over time. Assuming that the operating level N2 is 10%/m, the recovery level N1
If 5%/m is half of that, and the accumulation time is △t, the sensor of this invention starts the accumulation operation at time reading t1, and the smoke concentration reaches the recovery level at time reading t2 after Be1. As long as it is above N□, a fire alarm can be issued.

On the other hand, in a conventional sensor whose recovery level and operating level are the same, the accumulation operation starts from the time reading t3 when the smoke concentration changes by the operating level N2 or more, and Δ is not accumulated until the later time reading t4. A fire alarm will be issued, and the storage type fire detector of this invention can generate electricity early in the event of a fire.

In order to make the early detection of a fire sufficiently effective, it is desirable to select the hysteresis specification of the level determination circuit so that the recovery level /1/N1 is less than half of the operating level N2.

Figure 4 is a circuit diagram showing a concrete example of applying the storage type fire detector according to this invention to a photoelectric sensor using a scattered light method, and Figure 5 is a time chart showing the waveforms of each part. shows.

In FIG. 4, the sensor receives a constant DC voltage from a constant voltage circuit 18, and uses a light emitting diode LED as a light source.
This light-emitting diode LED includes a transistor Tr that is intermittently turned on and off at a constant cycle by an oscillator 20.
1 is blinking.

The scattered light caused by the flashing light of the light emitting diode LED is transmitted to the amplifier 2.
The photodiode PD connected to the input side of the photodiode 6 receives the light, converts it into an electrical signal, and connects it to the transistor Tr2 via a differentiating circuit made up of a capacitor C1 and a resistor R2.

A sample old circuit 22 is provided on the output side of the transistor Tr2.

The sample old 22 is turned on by the output of the oscillator 20, and the output of the transistor Tr2 is connected to the field effect transistor F.
A transmission gate G0 is used to transfer the detection signal to the ET, and a detection signal depending on the smoke concentration is extracted at the cycle of the oscillator 18, and is held in the capacitor C2.

Following this sample and hold circuit 22, a Schmitt trigger circuit 24 having a hysteresis characteristic for giving a recovery level different from the operating level is provided, and this sample and hold circuit 22 and Schmitt trigger circuit 24 form a level determination circuit. configured.

The shot trigger circuit 24 is connected to the input resistor R5 and the inverter ■1. ■ Connect 2 vertically and connect the resistor R6 from the output end.
If the elnsln type pressure is VDD, there is an input level eTH for inverting the output from L level to H level, and an input level for inverting the output from H level to L level. level e
TL is, however, VTH is given by the threshold voltage of the element itself.

Of course, the relationship is e TH > e TL.

The output of the Schmitt trigger circuit 24 is AND
is connected to one input terminal of the oscillator 20, and is taken out as a logical product with the output of the oscillator 20 applied to the other terminal, and is supplied to the storage circuit section 28.

In addition, in order to reset the storage circuit section 28 when the output of the Schmitt trigger circuit 24 becomes L level, an inverter 3 for inverting the output of the Schmitt trigger circuit and a reset signal oscillator from the inverter 3 are provided. A transmission gate G2 is provided for transmitting the signal to the reset terminal of the storage circuit section 28 in synchronization with the output of the storage circuit section 28.

As is clear from the time chart of FIG. 5, the operation of the embodiment shown in FIG. A differential output whose magnitude depends on the smoke density, indicated by the voltage at point ■, is generated at the terminal of Tr2.

This differential output charges and discharges the capacitor C2 through opening and closing of the transmission gate G1 in synchronization with the output of the oscillator 20, thereby producing a sample and hold output at the drain terminal of the field effect transistor FET.

When this sample hold output exceeds the eTH level, the hysteresis determination output of the Schmitt trigger circuit 24 is set from the L level to the H level, and is not reset unless the sample hold output falls below the eTL level.

At the early stage of a fire when the smoke concentration is low, the sample hold output will be below the eTL level, so the hysteresis judgment output will be reset, and there is a possibility that a certain number of operations will be performed to restore the accumulation operation that has started. However, if the eHL level is subsequently set to exceed the eHL level, and the state where it no longer falls below the e level continues for an accumulation time Δ, the accumulation circuit section 28 sends out a fire signal, turns on the thyristor SCR, and sends a signal to the receiver. In contrast, it sends out a fire alarm signal.

Fig. 6 shows another practical example in which this invention is realized with a dimming type fire detector, and the detection part 1 common to the circuit shown in Fig. 4 is shown.
0, the storage circuit 26, etc. are denoted by the same reference numerals, and the explanation thereof will be omitted.

Further, FIG. 7 is a time chart showing operation waveforms of each part in the embodiment of FIG. 6.

The difference between the attenuation type and the scattered light type is that a memory circuit 30 is provided following the sample and hold circuit 22, and this is capable of handling fluctuations in the brightness of the light source due to power fluctuations or temperature changes, changes in the sensitivity of the light receiving element, or is provided to prevent malfunction of the sensor due to attenuation of light due to dirt on the lens or reflecting mirror in the optical path.

That is, the memory circuit 30 is connected in parallel to the thread of the amplifier A3 which amplifies and transmits the detection signal extracted by the transmission gate G1. A thread path is provided for charging the capacitor C2 and taking out the charging voltage of the capacitor C2 as a storage output (0 point voltage) which becomes a reference voltage by an amplifier A2.

The Schmitt trigger circuit 24 following the memory circuit 30 uses a Schmitt trigger circuit having a differential amplifier configuration in which current feedback is wound from the output of the amplifier A4 via a resistor R9, and a sample hold output is input via a resistor R7. At the same time, the memory output is inputted as a reference voltage via the resistor R8.

Therefore, as shown in FIG. 1, when the difference between the storage output voltage va and the sample and hold output exceeds the magnitude of eTH, the amplifier A4 changes the output from the L level to the H level and starts the accumulation operation. When the difference between the sample hold output and the storage output voltage va becomes equal to or less than the magnitude of eTL, the output is inverted from the H level to the L level and the storage operation is reset.

FIG. 8 shows another actual case of the storage type fire detector of this invention, taking a scattered light type sensor as an example, and FIG. 9 shows a time chart of the operating waveforms of each part.

In this embodiment, a comparator is used in the level determination circuit 12 having hysteresis characteristics, and a comparator is used in the storage circuit 16.
It is characterized by using a counter.

First, looking at the level determination circuit 12, the transistor Tr2
The differential output of the detection signal taken out by comparator 3
2 and 34.

The comparator 32 has a reference level H that is a determination level for starting an accumulation operation, and when a detection signal exceeding the reference level H is input, the output is changed from a low level to a high level.

Further, the comparator 34 has a reference level L that is a determination level for restoring the storage operation once started, and when the detection signal becomes lower than this reference level L, the output high level up to that point is changed to a low level.

Therefore, the condition for starting the storage operation is that both outputs of the comparators 32 and 34 are at a high level, and the condition for restoring the storage operation is that both outputs of the comparators 32 and 34 are at a low level.

The output of the comparator 32 is applied to the clock terminal CL of a delay flip-flop (hereinafter referred to as D-F/F) via a delay circuit consisting of vertically connected inverters 4 and 5, and the output of the comparator 34 is It is applied directly to the terminal of F/F36.

Inverter ■4. ■The delay circuit consisting of 5 is D-F/F3
6, it is necessary to delay the CL terminal input by a predetermined time td from the D terminal input.

Therefore, when both the CL and D terminals become high level, the D-F/F 36 changes the output Q terminal from low level to high level and sends a counting pulse to the counter 38, and when the CL and D terminals become low level, The output Q terminal is again inverted to low level.

The reset signal for the counter 38 of the storage circuit 16 is
The output of the NOR gate NOR which takes out the inverted logical sum of the comparators 32 and 34 is applied and connected to the reset terminal of the counter 38 via the transmission gate G3.

The NOR gate NOR sends out a reset signal when both outputs of comparators 32 and 34 are at a low level.

This reset signal is transferred to the counter 38 at the timing of the gate reset of the transmission gate G3.

Oscillator 2 is connected to the gate of transmission gate G3.
0 of the inverter I6.0 constitutes a delay circuit. ■7
, and are connected via a monostable multivibrator 40 which is activated by the output of the inverter 7 and recovers after a certain period of time, and the gate pulse generation timing is determined by the oscillator output (O8C output), as is clear from the reset output in Figure 9. Monostable multivibrator 4 is activated at a timing approximately in the center of
A pulse with a time width determined by a time constant of 0 is supplied to the transmission gate G3.

In this embodiment, it is assumed that the count value is set so that the counter 38 of the storage circuit 16 generates an output when it counts four count pulses and turns on the thyristor SCR.

Next, the operation of the embodiment shown in FIG. 8 will be explained with reference to FIG. A high level is provided to the DF/F 36, but the output of the comparator 32 is still at a low level, so the DF/F 36 does not send a count pulse to the counter 38.

Next, when the detection signal exceeds the judgment level H of the comparator 32, the outputs of the comparators 32 and 34 become high level, the output of the D-F/F 36 changes to high level, and the counter 38 starts the first counting operation. let it happen.

Next, when the detection signal becomes lower than the determination level L of the comparator 34, a reset signal is supplied from the NOR gate NOR via the transmission gate G3, and the counter 38 that has started counting is reset.

Further, after the accumulation counting operation, when the detection signal is changing between the H level and the L level, neither the counting operation nor the reset operation for the counter 38 is performed.

If the detection signal continues to be at the H level or higher intermittently or continuously, the counter 3 will be counted in the fourth counting operation.
8 generates an output and turns on the thyristor SCR, causing the receiver to send out a fire signal.

The above embodiments have mainly been explained using photoelectric storage type fire detectors as an example, but other storage type sensors such as ionization type salt sensors can be similarly applied with hysteresis characteristics in the level judgment circuit. By keeping the fire in place, early detection of fires can be realized.

As explained above, the storage type fire detector of this invention has a circuit with a hysteresis characteristic in which the judgment level for resetting the accumulation operation once started is lower than the judgment level for starting the accumulation operation in the level judgment circuit. By using this method, once the accumulation operation has started, even if the detection signal level falls below the accumulation start level yv, if it is above the reset level, the accumulation operation will not be restored. Therefore, the accumulation operation is carried out in the early stages of a fire when the smoke concentration is low. It can complete the operation and solves the problem of difficulty in early detection of fire, which was a drawback of conventional storage type fire detectors, without sacrificing the advantage of fewer non-fire alarms.

[Brief explanation of the drawing]

Figure 1 is a graph showing the change in light attenuation rate over time using a smoke density meter obtained through experiments. Figure 2 is a block diagram showing the basic circuit configuration of this invention. Figure 3 is the change in smoke density over time. 4 is a graph diagram showing the operation of a level determination circuit with hysteresis characteristics in comparison with a conventional example; FIG. 4 is a circuit diagram showing a specific embodiment of this invention in a scattered light sensor;
5 is a time chart showing waveforms of various parts in the embodiment of FIG. 4, FIG. 6 is a circuit diagram showing another embodiment of this invention in a dimming type sensor, and FIG. 7 is a diagram of the waveform of each part in the embodiment of FIG. A time chart diagram showing the waveforms of each part in the embodiment, Fig. 8 is a circuit diagram showing another embodiment of this invention in a scattered light sensor, and Fig. 9 shows the waveforms of each part in the embodiment of Fig. 8. It is a time chart figure. 10...detection section, 12...level judgment circuit, 14...accumulation circuit, 16...alarm circuit, 18...constant voltage Circuit, 20...
・Oscillator (O8C), 22... Sample hold circuit, 24... Schmitt trigger circuit, 26
......Amplifier, 28...Storage circuit section, 3
0...Memory circuit, 32.34...Comparator, 36...Delay flip-flop (D-F/F), 38...Counter, 40...・
...Monostable multi-vibrator ~R1~R11''
``Resistor\C1・C2... Capacitor, Trl,
Tr2...Transistor, LED...
Light emitting diode, PD... photodiode,
G1. G2. G3...Transmission cable, ■, ~I7...Inverter, AND...
...And gate, NOR...Nor gate, A1-A4...Amplifier.

Claims (1)

[Claims for Utility Model Registration] A detection unit that detects physical changes in the surroundings, a level determination circuit that determines the output signal level from the detection unit, and an alarm after accumulating the output from the level determination circuit for a certain period of time. In a storage type fire sensor equipped with a storage circuit that generates an output, the level judgment circuit includes a circuit having a hysteresis characteristic in which a judgment level for starting an accumulation operation and a judgment level for restoring an accumulation operation once started are different. A storage type fire detector characterized by: