JPH044312Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] This invention relates to a fire alarm equipped with a device that warns of dirt on a fire sensor.

[Prior art]

Conventionally, a fire alarm system consists of a fire detector and a receiver that operate by detecting a predetermined amount of heat, light, or smoke caused by a fire.The receiver detects the operation of the fire detector and notifies the fire. was common.

However, in recent years, fire sensors have been used to detect fire phenomena such as heat, smoke, gas, or light caused by fires, and analog quantities converted to voltage and current are detected using repeaters or receivers. It was designed to control the fire extinguisher and evacuation guidance system. Furthermore, if an analog quantity smaller than the operating level of the device continues to occur for a predetermined period of time, it is detected and an indication that the fire sensor is contaminated is displayed.

[Problems with conventional technology]

However, with the fire alarms mentioned above, issuing a fire alarm is prohibited when a dirt alarm is issued, or the fire alarm is configured to issue both a fire alarm and a dirt alarm, so in the case of a smoldering fire, etc., the fire is lost. There were shortcomings such as making it difficult to tell which is correct, the fire alarm or the dirt alarm.

[Means for solving problems]

In consideration of the above points, the fire alarm of this invention is designed to reset the dirt alarm and notify the fire even in the case of a smoldering fire. A comparator for fire discrimination that detects a first predetermined value that is determined to be a fire out of the sent out analog output, and a second predetermined value that is smaller than the first predetermined value that is determined to be a contamination of the fire sensor. A dirt discrimination comparator that detects the value; a fire alarm switching circuit connected to the fire discrimination comparator and set by the output thereof;
A timer circuit is connected to the output of the comparator for dirt determination and outputs a dirt alarm when the output continues for a predetermined period of time, and the output of the switching circuit is connected to the reset terminal of the timer circuit to output the timer circuit. This resets the timer circuit.

[Effect]

Since the fire alarm of this invention has the above-mentioned characteristic configuration, even in the case of a smoldering fire, when the output of the fire sensor reaches a level that is determined to be a fire, the dirt alarm is reset and a fire alarm is issued.

〔Example〕

An embodiment of this invention will be described below with reference to the drawings. In Figure 1, S is an ion-type fire sensor, and the current increases or decreases depending on the potential at the connection point between the inner and outer ion chambers CH1 and CH2, which are equipped with a pair of electrodes and a radiation source, and both ion chambers CH1 and CH2. Amplifier A
It is constructed such that an analog voltage corresponding to the magnitude of the fire phenomenon is generated in the resistor R of the receiver RE.

IC1 is a comparator for fire discrimination, and fire sensor S
It is adjusted so that the analog output is inverted from "H" to "L" at the first predetermined value at which it is determined that there is a fire.IC2 is a D latch that transmits or latches the output of the comparator IC1 to the next stage. Its clock terminal is connected to current P12. B is a storage circuit provided to prevent receiver RE from malfunctioning due to cigarette smoke or electrical noise. IC3 is a switching circuit for fire alarm; Equipped with a Schmitt trigger function to invert the output of B.
NAND circuit G ₁ and a comparator for dirt determination described later
It is provided so that 〓H'' is output when IC5 and fire detection comparator IC1 operate together.
It consists of a NAND circuit _G2 and a flip-flop circuit consisting of two NOR circuits _G3 and _G4 which are set by this output. IC4 is a buffer circuit.
LED1 is a fire indicator light composed of light emitting diodes, and is lit in the event of a fire.

IC5 is a comparator for dirt discrimination, and the output of the comparator IC1 for fire discrimination is a second predetermined value smaller than the first predetermined value of the analog output from the fire sensor S, which is reversed from 〓H'' to 〓L''. The output is 〓H”
It is adjusted so that it is reversed from "L" to "L".
Similar to IC2, IC6 is a D latch that transmits or latches the output of comparator IC5 to the next stage. Its clock terminal is connected to current P12, and its Q output is connected to a switching circuit.
It is connected to the NAND circuit _G2 and NOR circuit _G4 of IC3. IC7 is a NAND circuit, and the subsequent timer circuit
The IC8 is set so as to be set by the ``H'' output of the IC6, and reset by the ``L'' output of the IC3. IC8 is a timer circuit provided to temporally determine whether the change in the output of the fire sensor S is due to fire or dirt. It consists of an oscillator, etc., and is set by the 〓L'' input, and after a predetermined time, its output becomes 〓
It changes from “L” to “H”.

Tr is a transistor for detecting an abnormality such as a short circuit in the output of the fire sensor S, and is configured to be turned on in a normal state and turned off in a short circuit state, and its collector is connected to the transistor Tr'.
The collector of the transistor Tr' is connected to the timer circuit IC8.
The output is connected to the NOR circuit IC9, and the output is connected to the operation indicator LED2 composed of a light emitting diode through the NAND circuit IC10.
The light is turned on when the fire sensor S is normal. Further, in FIG. 1, P20 is supplied with 20V power from a power source not shown, and P12 is supplied with 12V power.

Next, the operation of the fire alarm will be explained.

When the power is turned on, 20V power is supplied to the fire sensor S, and 20V and 12V power are supplied to each circuit element of the receiver RE. Furthermore, when the above fire sensor S is installed, there is no accumulation of dust and the function is maintained normally, so the outputs of the comparator IC1 for fire discrimination and the comparator IC5 for dirt discrimination are both 〓 H”,
The outputs of the D latches IC2 and IC6 become ``L''. As a result, the storage circuit B ``L'', the switching circuit IC3 ``H'', and the buffer circuit IC4 become ``H'', and the fire indicator light LED 1 is turned off. Also
NAND circuit IC7〓H”, timer circuit IC8〓L”,
NOR circuit IC9〓H”, NAND circuit IC10〓L”
Then, the operation indicator light LED2 lights up, indicating that the fire sensor S is continuing to monitor normally.

When a fire occurs and smoke flows into the external ion chamber CH2, the voltage drop across the resistor R of the receiver RE becomes curve f in Figure 2.
When the fire discrimination level (first predetermined value) is exceeded, the comparator IC1 changes from 〓H'' to 〓
As a result, the output of the D latch IC2 changes to ``H'', and the capacitor of storage circuit B is charged, and becomes ``H'' after a predetermined time.As a result, the fire alarm switching circuit IC3 changes to ``L'' and the buffer Circuit IC4 becomes 〓L” and the fire indicator LED turns on.
1 is lit to indicate that a fire has occurred.
In this case, the comparator IC5 for dirt discrimination is also inverted from ``H'' to ``L'', and the output of the D latch IC2 is also inverted from ``L'' to ``H'', and the NAND circuit IC
7 sets the timer circuit IC8, but in the event of a fire, the switching circuit IC3 is immediately reversed from ``H'' to ``L'', so the NAND circuit IC7 becomes ``H'' and the timer circuit IC8 is reset. .

In addition, in a smoldering fire as shown in curve f' in Figure 2, the output of the fire sensor S exceeds the dirt discrimination level (second predetermined value) at time _T1 , and the comparator IC5
is reversed from 〓H'' to 〓L''. As a result, D
The output of latch IC6 becomes 〓H” and NAND circuit
IC7 becomes ``L'' and sets timer circuit IC8, and after a predetermined time, its output becomes ``H''. This causes the operation indicator LED to appear through circuits IC9 and IC10.
Turn off 2. However, at T ₂ hours, the output of the fire sensor S exceeds the fire discrimination level (first predetermined value), so the comparator IC
1 becomes ``L'', the output of D latch IC2 becomes ``H'', the storage circuit B becomes ``H'', and the switching circuit IC3 for fire alarm becomes ``L''. As a result, the fire indicator light LED1 is turned on via the buffer circuit IC4 to notify of a fire. Also switching circuit IC3
The NAND circuit IC7 becomes ``H'' due to the ``L'' output, the timer circuit IC8 is reset, and the operation indicator LED 2 is turned on, so that it can be determined that the fire sensor S has detected a fire based on its normal function.

Also, due to dirt in the ion chamber CH2 of the fire sensor S, the voltage drop across the resistor R gradually increases until it reaches a second predetermined value that inverts the comparator IC5 for dirt discrimination, and its output changes from 〓H'' to 〓L''. If the output is reversed, the output of the fire sensor S reaches the fire discrimination level (first predetermined value) within a short period of time, and the comparator IC1
Since the timer circuit IC8 is not inverted to ``L'', the timer circuit IC8 remains set, and its output becomes ``H'' after a predetermined time. As a result, the NOR circuit IC9 becomes L, the NAND circuit IC10 becomes "H", the operation indicator LED2 is turned off, and the fire sensor S
is dirty or malfunctioning.

In the above embodiment, D latches IC2 and IC6 are provided to latch the outputs of comparators IC1 and IC5 so that the functions are maintained even if the power is momentarily cut off, and a storage circuit B is provided to prevent malfunction due to cigarette smoke. In addition, a NAND circuit _G1 was provided in the switching circuit IC3 for matching with these outputs.
If these are not needed, comparators IC1 and IC5
The switching circuit IC3 may be set or reset by the output directly or via an inverter. Furthermore, although the above embodiment has been described as a receiver, a repeater may be used, and the fire sensor may also be of a thermal type or a photoelectric type.

〔effect〕

The fire alarm system of this invention is configured and operates as described above, so even in the case of a smoldering fire where the output of the fire sensor gradually changes, the fire alarm system issues a fire alarm and prohibits alarms for dirt, etc. There is an effect that can be obtained by machine.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the fire alarm of this invention, and FIG. 2 is an output waveform diagram of the fire sensor. S...Fire sensor, RE...Receiver, IC1, IC
5... Comparator, IC3... Switching circuit, IC
7...NAND circuit, IC8...timer circuit.

Claims (1)

[Scope of utility model registration request] The receiver or repeater includes a comparator for fire discrimination that detects a first predetermined value that is determined to be a fire among the analog outputs sent from the fire sensor to the receiver or repeater; a comparator for dirt discrimination that detects a second predetermined value smaller than the first predetermined value to be determined; and a switching circuit for fire alarm connected to the comparator for fire discrimination and set by the output thereof. and a timer circuit that is connected to the output of the comparator for dirt discrimination and outputs a dirt alarm when the output continues for a predetermined period of time.
A fire alarm system further characterized in that the output of the switching circuit is connected to a reset terminal of the timer circuit, and the timer circuit is reset by the output.