JPS6358591B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a fire detection device attached to an automatic fire extinguishing system.

[Prior Art] As shown in FIG. 1, a heat sensor used in a conventional fire detection device has a cover 2 on a housing 21.
A contact 23a is formed on the diaphragm 24 disposed in the heat sensitive chamber 26.
On the other hand, the housing 21 supports the contact 23 facing the contact 23a via an insulator, and the housing 21 is provided with a narrow passage or leak hole 22 that communicates the heat sensitive chamber 26 with the outside. .

Due to air expansion in the heat sensitive chamber 26, the diaphragm 24
When the contact 23a is pushed up, the contact 23a comes into contact with the contact 23, and the control valve of the automatic fire extinguishing system, specifically the control valve disposed in the conduit connecting the fire extinguishing agent tank and the fire extinguishing agent discharge nozzle, opens and the fire extinguishing agent is released. In this heat sensor, the distance between the contacts 23 and 23a is adjusted so that when the temperature of the heat sensitive chamber 26 rises at a predetermined temperature increase rate, the contacts 23 and 23a close. Early detection of fire is difficult due to the long response time of contact operation due to expansion.

Further, as shown in FIG. 2, a heat sensitive chamber 37 covered by a cover 35 is formed in the housing 31,
A thermocouple 36 is disposed on the protrusion of the cover 35 with the hot junction 36b on the outside and the cold junction 36a on the inside, and a relay coil 34 connected to both of these contacts and a movable contact 33 that is opened and closed thereby generate a relay. A configuration in which the switch 32 is configured has also been proposed. Although this has excellent responsiveness to changes in ambient temperature in the event of a fire, the relay 34 is energized and the contact 33
In order to close the sensor, a large rate of increase in ambient temperature is required, making it difficult to obtain high sensitivity.

Heat-sensitive elements with excellent responsiveness and high sensitivity are already known, but when such elements are used as heat detectors in fire extinguishing equipment, there are many chances of malfunction, which poses a practical problem.

However, in factories, such as semiconductor manufacturing factories, where buildings are shielded from the outside and have heat treatment processes and cleaning processes that handle combustible materials, the risk of fire outbreaks is high, and it is difficult to detect fire outbreaks quickly and accurately. is desired. Generally, the heat and gas discharged from the heat treatment process and the cleaning process are exhausted to the outside through a common duct, so it is best to install the heat sensor inside the duct. In this case, the temperature inside the duct is affected by the heat discharged from the heat treatment process, so the temperature change due to a fire occurring inside the clean bench that makes up the cleaning process and the temperature change due to exhaust heat from the heat treatment process are If it cannot be determined, the automatic fire extinguishing system will malfunction.

[Problems to be Solved by the Invention] Therefore, an object of the present invention is to accurately detect a fire by determining from the signal of a heat sensor whether it is a real fire or a temperature rise due to exhaust heat from factory equipment.
An object of the present invention is to provide a fire detection device.

[Means for Solving the Problem] In order to achieve the above object, the present invention includes a differentiating circuit that differentiates the detection signal of the heat sensor, and a comparison circuit that compares the output signal of the differentiating circuit with a reference signal of a predetermined level. It consists of a circuit and an adder that adds an output signal of a predetermined level from the differentiating circuit and an output signal of a predetermined level opposite to the output signal of the differentiating circuit from a multivibrator driven by the output signal of the comparator circuit. , the output signal of the adder is used as a fire signal.

[Function] The detection signal of the heat sensor is differentiated by differentiating circuits 2, 3, and 4, and this signal is compared with a reference signal in comparator 7. When the signal exceeds the reference signal, comparator 7 outputs a predetermined level for a certain time. is output as a positive signal. The multivibrator 9 driven by the signal from the comparator 7 generates a negative signal at a predetermined level and for a predetermined time (pulse width). The adder 13 adds the comparator output signal and the multivibrator signal, and when the duration of the comparator signal is greater than the signal from the multivibrator, the adder 13 sends a fire signal to the fire extinguishing system. It will be done.

Therefore, even if a temperature change unrelated to a real fire is detected from the ambient conditions of the heat sensor, a real fire will only be determined if the detection signal continues for a predetermined period of time at a predetermined level of temperature rise rate. , thereby avoiding malfunction of the fire extinguishing system.

[Embodiment of the Invention] In FIG. 3, 1 is an input terminal connected to a heat sensor (not shown), 2 is a capacitor, 3 is a resistor, 4 is an operational amplifier, 6 is a reference voltage setting resistor,
7 is a comparison amplifier, 9 is a monostable multivibrator, 10 is a resistor, 11 is a capacitor, 13 is an adder, and 14 is a signal for operating a control valve of a fire extinguishing device, such as a fire extinguishing agent tank, based on a fire occurrence signal. This is an output terminal that generates.

In the above configuration, the capacitor 2, the resistor 3, and the operational amplifier 4 constitute a differentiating circuit, which differentiates the signal change from the heat sensor that detects the ambient temperature, that is, the signal change as shown in FIG. Then, a differential value as shown in FIG. 4b is output. This differential value is compared with a reference voltage set by a resistor 6 in a comparator amplifier 7, and when the differential value exceeds the reference voltage, an output voltage as shown in FIG. 4c is generated at a terminal 8. This output voltage is applied directly to the adder 13 and also to the monostable multivibrator 9.

The monostable multivibrator 9 is equipped with a resistor 10 that sets the value of the input voltage that drives it.
With an input signal above a predetermined level, the predetermined pulse width n determined by the capacitor 11 (Fig. 4d)
An output signal of is generated from terminal 12 and added to adder 13
It is now being added to

In the adder 13, when the duration m (FIG. 4c) of the output signal of the comparator amplifier 7 is larger than the pulse width n of the monostable multivibrator 9, the output terminal 1
4, a fire signal is generated as shown in Figure 4e.

The ambient temperature where a heat detector is installed changes due to the effects of heat generated from factory equipment, etc., regardless of the fire. If the temperature rise rate is high but the duration is short, as shown by curve s in Figure 4a, it is determined that this is not due to a fire but to the effect of temporary heat generated from factory equipment, and the adder 13
does not generate a fire signal e to the fire extinguishing system.

On the other hand, if the temperature increase rate is higher than a predetermined level and its duration is long, as shown by curve u in FIG. Further, by comparison with the signal from the monostable multivibrator 9, it is determined that the temperature rise continues for a predetermined period of time. Based on both of these conditions, the adder 13 sends the fire signal e to the fire extinguishing system. Therefore, even if the ambient temperature around the heat sensor temporarily increases due to exhaust heat from the factory, the accident of generating a fire signal and causing the fire extinguishing system to malfunction can be avoided. If the ambient temperature rises rapidly and continues for a predetermined period of time or more, a fire signal is sent to the fire extinguishing system, and the fire extinguishing system is activated.

[Effects of the Invention] As described above, the present invention includes a differentiating circuit that differentiates the detection signal of the heat sensor, a comparison circuit that compares the output signal of the differentiating circuit with a reference signal of a predetermined level, and a predetermined level output signal from the differentiating circuit. and an output signal of a predetermined level opposite to the output signal of the differentiating circuit from the multivibrator driven by the output signal of the comparator circuit, and the output signal of the adder is used as the fire signal. Therefore, even in an environment where the ambient temperature changes due to exhaust heat from factory equipment, etc., a fire can be detected accurately at the early stage based on the temperature rise rate and the duration of the rise at a relatively low temperature. detected and malfunction of the fire extinguishing system is avoided.
In particular, even in environments affected by exhaust heat from factory equipment,
Since there is no need to set the temperature of the heat detector higher than the ambient temperature, fires can be quickly detected before the fire gets too strong, and damage can be minimized.

[Brief explanation of drawings]

Fig. 1 is a side sectional view of a conventional heat sensor, Fig. 2 is a side sectional view of another conventional heat sensor, Fig. 3 is a circuit diagram of a fire detection device according to the present invention, and Fig. 4 is the same. FIG. 3 is a diagram illustrating the operation of the device. 1: Input terminal, 2: Capacitor, 3: Resistor,
4: operational amplifier, 7: comparison amplifier, 9: monostable multivibrator, 13: adder, 14: output terminal.

Claims (1)

[Claims] 1 A differentiation circuit that differentiates the detection signal of the heat sensor,
A comparison circuit that compares the output signal of the differentiation circuit with a reference signal of a predetermined level, an output signal of the predetermined level from the differentiation circuit, and an inverse output signal of the differentiation circuit from a multivibrator driven by the output signal of the comparison circuit. 1. A fire detection device comprising: an adder for adding output signals of a predetermined level to an output signal of a predetermined level, the output signal of the adder being used as a fire signal.