JPH03271898A - Fire sensor - Google Patents

Abstract

PURPOSE:To facilitate a construction and to automatically detect trouble by sending the output of a measuring circuit, which measures the resistance value of a sensing line made of a metallic wire at intervals of a certain time, to a receiver. CONSTITUTION:The temperature rise value of a sensing line 1 is decided by a deciding circuit 7 in accordance with the series of the resistance value sent from a time series storage circuit 5, and the deciding circuit 7 not only decides the temperature rise value for one past minute but also calculates the moving average value of a temperature rise rate to perform decision or abandons an especially exceptional measured value by a rejection test to systematically decide a fire, non-fire, or a disconnection accident. It is decided by the deciding circuit 7 whether a fire occurs or not in accordance with temperature rise information, and the information is sent to the receiver of a fire alarm. Thus, the construction is facilitated and trouble of a disconnection accident is automatically detected.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a fire detector that detects room temperature not at a point but at a surface using heat-sensitive elements distributed over a wide range.

(0) Conventional technology Conventional spot-type fire detectors that detect fires at a single point are sensitive to fires that occur directly below them, but are sensitive to fires that occur horizontally away. sensitivity decreases rapidly.

A distributed type fire detector that eliminates the drawbacks of the spot type fire detector was also sold, but this uses an air tube made of copper pipe with an inner diameter of about 2 mm as a heat-sensitive element, and this air tube is attached to the ceiling. Special techniques were required to avoid crushing the pipe during installation.

Furthermore, it is not possible to automatically detect when the air pipe becomes useless due to being crushed or punctured by an external force. Another attempt was to use a wire-shaped heat-sensitive semiconductor, but the sensitivity was poor (weak against radio wave interference, etc.).

(c) Problems to be Solved by the Invention In the event of a fire, the fire detector operates as a fire detector with little difference in sensitivity depending on the location where the fire occurs, is easy to construct, and can automatically detect failures such as wire breaks.

(:) Means for Solving the Problem In order to average the room temperature, heat-sensing elements (hereinafter referred to as sensing wires) made of metal resistance wire are widely distributed in a linear manner.

A relatively large amount of power is passed through the resistance wire to increase detection sensitivity. In order to reduce this power consumption, we use intermittent energization rather than constant energization, and detect the room temperature through sampling.

(Book) Function The sensing wire attached to the ceiling or wall is heated or cooled by the indoor air, and exhibits a resistance value depending on the temperature at that time. The temperature coefficient of this resistance value shows a constant value over a wide range in the case of highly pure metals, so
It is easy to calculate the temperature increase rate from the resistance value.

The value of this temperature rise rate is compared with the value stipulated in the national standards for fire detectors to determine whether there is a fire or not.

The current standard specifies that a fire alarm will be issued if a 20m section of the sensing line is exposed to a temperature rise of 10°C/min for 1 minute.

(f) Example Embodiments of the present invention will be described with reference to the drawings.

Figure 1 is a plan view showing a case where a sensing line and a detector are installed in one building, where 1 is the sensing line and 2 is the detector.

3 indicates the wall of the building. Note that A is a room to be guarded, and B is a corridor that is separated by ceilings, walls, etc.

FIG. 2 is a front view showing the internal configuration of the detector 2. As shown in FIG.

In Fig. 2, 4 is a circuit for measuring the resistance of the sensing line 1;
6 is a time series memory circuit that stores measured resistance values as time series values at regular intervals for a certain period of time, for example, 5 minutes; 6 is a time series memory circuit that processes signals sent from the time series memory circuit 5; A circuit that calculates the rate of temperature change from the rate of change in resistance; 7 is a circuit that compares the temperature rise rate from calculation circuit 6 with a built-in reference value to determine whether there is a fire or not; 8 is a circuit that determines the determination result. The circuit for sending data to the receiver, 9, is a sampling circuit for reducing current consumption.

In FIG. 1, the sensing line 1 is placed on the ceiling, or on the wall in some cases, so that no location in the room is more than a few meters away from the sensing line 1 on the plan of the building. Because it is so-called exposed wiring, it is easy to rearrange it after installation by changing the partitions of the building, etc.

A pure metal wire is recommended for the sensing wire 1 because of its high temperature coefficient of resistance, and pure nickel wire is particularly excellent because of its high temperature coefficient, corrosion resistance, and relatively high resistivity. What is the resistivity of pure nickel? , 24×10−”Ω·m, and the temperature coefficient of resistivity is 6.7×10−”/”C.

Nickel wires of about 0.1 to 0.5 mm are covered with an insulator and used as two stranded wires. Use a regular metal wire, not a hollow vibrator, so that the metal wire is resistant to blows and shocks.

For example, in the case of two bare nickel wires in a room with a diameter of 0.2 mm (total length 100 m x 2), the resistance increases by 3.09 Ω every time the temperature rises by 1°C over the entire length. The rate of increase is approximately constant between -100°C and 300°C.

One end of the sensing wire 1 is short-circuited by soldering or the like to form a loop. In the example of FIG. 1, this end is shorted at the end of the hallway.

The two other ends of the looped pair of sensing wires 1 are attached to the two terminals of a detector 2, and a current is applied intermittently, for example every few seconds, to measure the resistance.

Since the material and diameter of the sensing wire are determined at the time of manufacture, the increase in resistance per unit temperature of the sensing wire 1 per unit length is known in advance.

The absolute value of the resistance value of the sensing wire 1 changes depending on the total length of the sensing wire 1 and the room temperature at that time, but when used as a fire detector, the current national standard stipulates that the total length is 100 m or less, Regardless, it is stipulated that whether there is a fire or not is judged based on the rate of temperature rise in a 20m section, so the absolute value of resistance does not matter, but the relative rate of rise in resistance, that is, the rate of temperature rise. If only this is known, it can be used as a fire detector. As an example, when the temperature of a pair of 0.2 mm diameter sensing wires of 20 m in length increases at a rate of 10° C. for 1 minute, the increase in the resistance value of the sensing wire l is expressed by the following equation.

7.24X 10-”ΩmX 40mX 6.7X 1
0-”/”e X 10℃/+aX1myr X
(0,1x 10-”) “m” ~ 6.17Ω Therefore, from the series of resistance values sent out from the time-series memory circuit 5, the temperature rise value that the sensing wire 1 is receiving is determined by the determination circuit 7 as described above. It can be done.

The determination circuit 7 not only makes a determination based on the temperature rise value for the past minute, but also calculates the moving average value of the temperature increase rate and performs a rejection test to reject particularly prominent measured values. A comprehensive judgment is made as to whether there is a fire, non-fire, or a disconnection accident.

This temperature rise information is judged by the judgment circuit 7 as to whether or not there is a fire, and is sent by the signal sending circuit 8 to a fire alarm receiver (not shown).

In order to improve the S/N, it is better to have a large amount of power flowing through the sensing wire l, and in the case of the aforementioned 0.2 mm paired loom sensing wire, it is 20 to 30 mA, 0.18 to 0.4
W rank is good. In the case of a large building, the number of detectors 2 is large even with this level of power, so the thickness of the wiring becomes a problem, so a sampling circuit 9 is used to save power and wiring costs. The sampling interval may be approximately once every few seconds.

In the case of a wire breakage, the resistance value increases extremely and the calculated temperature becomes extremely high, which is easily automatically detected and sent to the receiver.

Although each device circuit is described as being independent in the above description, the invention is the same even if these are realized by each circuit such as a microcomputer or LSI.

3 and 4 show another embodiment of the invention.

In the above-mentioned detector, a determination circuit 7 was installed inside the detector to determine whether there was a fire or not, but the detector only had a resistance value or not.
Alternatively, it is also useful to detect only the temperature change value calculated from this, send it to the receiver together with the unique number of the sensor, and then determine whether there is a fire or not. FIG. 3 shows an example in which the time series storage circuit 5, temperature change rate calculation circuit 6 and determination circuit 7 are removed, and FIG. 4 shows an example in which only the determination circuit 7 is removed.

In these cases, the circuitry in the sensor is simplified and cheaper, but the receiver is more complex and expensive.

FIG. 5 shows still another embodiment, in which a bridge circuit port and a resistance change measuring circuit 16 are used in place of the resistance measuring circuit 4 described above.

The rate of temperature rise that the detection line should detect in the event of a fire is 10°C/m, but annual temperature changes and temperature differences between cold and hot regions range from -40°C to +60°C. Therefore, the temperature change of the sensing line due to air temperature is greater than the temperature rise of the fire to be detected.

Of course, the temperature increase due to air temperature is large in absolute value (but in terms of rate of increase, it is much smaller than in the case of a fire.

The bridge circuit shown in FIG. 5 is used to cancel the influence of resistance changes in the sensing wire due to temperature changes and to detect only the resistance change rate with a high S/N ratio. At the bridge circuit port, 1 is a sensing wire, 11 is a resistor made of a material that has the same temperature coefficient of resistance as the sensing wire, and 12 and 13 are resistors that have a much lower rate of change in resistance due to temperature than the sensing wire. For example, resistors made of manganin wire or resistors with the same temperature coefficient of resistance, the three resistors 11, 12, and 13 are placed inside the detector and placed in a container isolated from the outside with thermal insulation. It is stored. In this way, the sensing wire is exposed to the outside air, so it responds sensitively to temperature rises in the event of a fire, but since the other three resistors are surrounded by thermal insulation, the time constant of temperature change is It is extremely large and cannot keep up with rapid temperature changes such as the rise in temperature during a fire. However, since it follows slow changes such as temperature changes, if such a bridge is constructed, only changes due to rapid temperature rises, such as the temperature rise of a fire, will appear between the detection terminals 14 and 15 at the bridge entrance. S/'N becomes good. The variable resistor 11 of the bridge H is adjusted so that the potential difference between the bridge and bridge detection terminals 14 and 15 becomes close to zero after the construction of the Ichi Line 1 is completed and its total length is determined.

The resistance change measuring device 16 is mainly composed of a digital voltage measuring device with a high input resistance, and measures the resistance change of the sensing wire from the potential difference appearing at the detection terminals 14 and 15 every time the sampling circuit 9 operates. Do it every time.

This bridge system is very effective in improving S and /N.

(g) Effects of the invention The present invention produces the following effects.

Construction is easier than conventional air tube type distributed fire detectors. Resistant to mechanical shock. Easy to rearrange after installation. Critical point failures such as disconnection accidents can be automatically detected. Since the information from the detectors can be centrally managed by a central receiver, it is possible to accurately determine the occurrence of a fire and its subsequent development. Therefore, information for fire evacuation can be more reliable.

Compared to conventional spot-type detectors, it detects temperature rises over a wide range of rooms on average, allowing for more accurate fire detection. It is cheaper than the conventional air tube type.

As described above, the present invention has many effects and is extremely useful.

[Brief explanation of drawings]

Fig. 1 is a plan view of a building when the fire detector of the present invention is installed in the building, Fig. 2 is a block diagram showing an embodiment of the present invention, and Figs. 3 and 4 are block diagrams showing other embodiments. FIG. 5 is a diagram showing a resistance change measuring portion of the present invention. l... Sensing line 4... Resistance measurement circuit 5... Time series memory circuit 6... Temperature change rate calculation circuit 7... Fire/non-fire determination circuit 8... Signal sending circuit 9...・Sampling circuit H...Bridge circuit 16...Resistance change measurement circuit Fig. 1

Claims (4)

[Claims] (1) Sensing wires made up of metal wires distributed on the ceiling of the guarded space, a circuit that measures the resistance of the sensing wires at regular time intervals, and sends the output of the measuring circuit to a receiver. A fire detector characterized by being equipped with a signal sending circuit. (2) A sensing line consisting of metal wires installed distributed on the ceiling of the guarded space, a circuit that measures the resistance value of the sensing line at regular time intervals, and the output of the measuring circuit as a time series value. A fire detector comprising a time series memory circuit for storing data, a circuit for calculating a temperature change rate from the output of the memory circuit, and a signal sending circuit for sending the output of the calculation circuit to a receiver. (3) A sensing line consisting of metal wires distributed on the ceiling of the guarded space, a circuit that measures the resistance value of the sensing line at regular time intervals, and the output of the measuring circuit as a time series value. A time series memory circuit for storing data, a circuit for calculating a temperature change rate from the output of the memory circuit, and a circuit for comparing the temperature change rate from the calculation circuit with a built-in reference value to determine whether or not there is a fire. A fire detector comprising: a signal sending circuit for sending the output of the determination circuit to a receiver. (4) In place of the resistance measuring circuit, a bridge circuit having a heat sensing line on one side and a circuit for measuring a change in resistance from the output of the bridge circuit at regular time intervals is provided. Or the fire detector described in 2 or 3.