JP2024113715A - Fire detectors and fire alarm systems - Google Patents

Abstract

[Problem] To provide a fire detector that allows the fire receiver to detect or detect the presence of a reverse-connected fire detector without requiring major changes to specifications or increased costs, and a fire alarm system using the fire detector. [Solution] In a fire detector having a common terminal and a line terminal connected to a common wire and a line wire that constitute a signal line, and receiving power from a fire receiver via the signal line, two Zener diodes are connected in series in opposite directions between the common terminal and the line terminal, and one of the two Zener diodes has a Zener voltage higher than the DC voltage of the power supply, and the other Zener diode has a Zener voltage lower than the DC voltage of the power supply. [Selected Figure] Figure 2

Description

The present invention relates to a fire detector and a fire alarm system, and in particular to a fire detector and a fire alarm system that can grasp the state of a wiring error, such as a reverse connection, that occurs during installation work before the start of actual operation.

When installing a fire alarm system, wiring that will serve as the circuits connecting the detectors to the fire receiver is laid in the ceiling or other space above the monitored area, and an appropriate number of fire detectors are then connected to each circuit. Here, the internal circuits of the fire detectors that are connected to the circuits have polarity, so when carrying out the above work, the detectors must be connected with the correct polarity (positive connection) to the two signal lines that make up each circuit, known as the L line (line line) and C line (common line). This is because the power required for the detectors to operate is supplied from the signal lines, with the L line acting as the power line and the C line acting as the ground line.

However, there is a risk that the L and C terminals on the detector side may be connected in reverse to the L and C lines of the line due to a human error during installation work. Even if the detectors are connected in reverse, it is possible to provide protection circuits in each detector to prevent damage to the internal circuitry of the fire detector, or to prevent the internal circuitry from operating; however, if the detector does not operate, no fire will be detected, and the receiver will not be aware of the reverse connection, which could lead to the condition being left unattended.

Patent Document 1 discloses a technology for fire detectors that makes the detector non-polarized from the signal line by providing a diode bridge circuit with a rectifying function between the L and C signal lines and the detector, allowing it to operate in the same way as if it were connected correctly even if it is connected in reverse. Patent Document 1 also describes connecting a pair of Zener diodes for surge absorption in series between the L and C terminals in the opposite directions.

Japanese Utility Model Application Publication No. 02-006391

A fire detector equipped with a diode bridge circuit as described in Patent Document 1 has the problem that the number of elements is increased, resulting in increased costs, and while the voltage applied to the inlet terminal of the detector does not change, the voltage applied to the circuit operating inside the detector is lowered, which may prevent the fire receiver from accurately determining whether or not there is a fire.
In addition, in a data transmission type fire alarm system that transmits and receives data between the fire receiver and the detector via the detector line, it is possible to provide the fire receiver with a function to transmit a new signal to detect or understand the reverse connection of the detector. However, adding such a function requires modification of the fire receiver, which poses the problem of inviting major specification changes and increased costs.

The present invention was made with a focus on the above-mentioned problems, and its purpose is to provide a fire detector that allows the fire receiver to detect or detect the presence of a reverse-connected fire detector without requiring major changes to specifications or increasing costs, and a fire alarm system that uses the fire detector.

In order to achieve the above object, the present invention provides
A fire detector having a common terminal and a line terminal connected to a common line and a line line constituting a signal line, and receiving power from a fire receiver via the signal line,
Two Zener diodes are connected in series between the common terminal and the line terminal in opposite directions;
One of the two Zener diodes has a Zener voltage higher than the DC voltage of the power supply, and the other Zener diode has a Zener voltage lower than the DC voltage of the power supply.

According to a fire detector configured as described above, when the common and line wires are reverse-connected to the common and line terminals, current flows through the two Zener diodes, and the resulting change in current or voltage can be detected on the fire receiver side via the signal wire, so that the fire receiver side can detect or know the reverse connection state of the detector by using a signal that is already adopted as a specification for the fire alarm system. Therefore, the presence of a reverse-connected fire detector can be detected or known on the fire receiver side without adding a function to generate a new signal, that is, without incurring major changes to specifications or increasing costs.

Another invention of the present application is
A fire detector having a common terminal and a line terminal connected to a common line and a line line constituting a signal line, and receiving power from a fire receiver via the signal line,
A constant current diode through which a predetermined current flows when a DC voltage of the correct polarity and the opposite polarity from the power supply is applied is connected between the common terminal and the line terminal.

In a fire detector configured as described above, when the common and line wires are reverse-connected to the common and line terminals, a current flows through the constant current diode, and the resulting change in current or voltage can be detected on the fire receiver side via the signal line (detector line). Therefore, the reverse connection state of the detector can be detected or understood on the fire receiver side by using a signal that is already adopted as a specification for the fire alarm system.

Here, it is preferable that a Zener diode having a Zener voltage higher than the DC voltage of the power supply is connected in series with the constant current diode in a reverse direction between the line terminal and the common terminal.
With this configuration, it is possible to detect or grasp the reverse connection state of the sensor, while protecting the internal circuit of the sensor from surge voltages by the high-voltage Zener diode connected between the line terminal and the common terminal.

Another invention of the present application is
A fire detector having a common terminal and a line terminal connected to a common line and a line line constituting a signal line, and receiving power from a fire receiver via the signal line,
Between the common terminal and the line terminal, an indicator means which lights up when a DC voltage of a polarity opposite to the correct polarity is applied from the power supply, and a Zener diode having a Zener voltage higher than the DC voltage of the power supply are connected in series.

In a fire detector having the above configuration, when the common and line wires are reversely connected to the common and line terminals, the display means lights up, allowing an operator to visually determine the reverse connection state of the detector. In addition, the high-voltage Zener diode connected between the line and common terminals can protect the internal circuitry of the detector from surge voltages.

Further, another invention of the present application is a fire alarm system including a fire detector configured as described above and a fire receiver that notifies an occurrence of a fire when a predetermined voltage signal or current signal is input from the fire detector via the signal line,
The fire receiver includes:
When a voltage signal or a current signal indicating the occurrence of a fire is input from the signal line immediately after power is turned on in a state in which a plurality of the fire detectors are connected to the signal line, the fire occurrence is notified, and
The device is configured to determine that the common terminal and line terminal of any of a plurality of fire detectors connected to the signal line are reversely connected to the common line and line line, and to notify of the reverse connection.

In a fire alarm system configured as described above, if the common and line wires are reversely connected to the common and line terminals of the detector, the fire receiver detects this and notifies the user, making it easy to know that a connection has been made incorrectly during the detector installation process and to correct the connection to the correct state.

The present invention has the advantage that the presence of a reverse-connected fire detector can be detected or detected on the fire receiver side without adding a function for generating a new signal, and therefore without incurring major changes to specifications or increasing costs.

1 is a system configuration diagram showing a schematic configuration of a fire alarm system to which the present invention is applied. 1A to 1E are circuit diagrams showing an embodiment of an internal circuit of a fire detector connected to a signal line. 1 is a system configuration diagram showing an example of a reverse connection state of a detector in a fire alarm system including a fire detector of an embodiment.

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.
FIG. 1 shows a schematic configuration of a fire alarm system to which the present invention is applied.
As shown in Fig. 1, the fire alarm system is composed of a fire receiver 11, a plurality of fire detectors 13 connected between a line (L line) 12A and a common line (C line) 12B that constitute a signal line as a detector line extended from the fire receiver 11, and a termination resistor 14 connected between the ends of the L line and the C line. Each fire detector 13 receives a DC voltage, for example, DC 24V, from the fire receiver 11 via the signal lines 12A and 12B. Although Fig. 1 shows a pair of signal lines and a plurality (three) of fire detectors connected to the signal lines, in a building, for example, a signal line is installed for each floor and a fire detector is connected to the signal line.

2A to 2E show examples of the internal circuitry of the fire detector 13 connected to the signal line.
2(A) is provided with Zener diodes ZD1 and ZD2 connected in series in the opposite directions between the L terminal 31A and the C terminal 31B, a detector internal circuit 32 having a fire detection function, and a diode D1 for preventing reverse current connected in series with the detector internal circuit 32. The Zener diode ZD1 is a protective element for protecting the elements constituting the detector internal circuit 32 by passing a reverse current when a high voltage is applied, and an element having a high Zener voltage, for example 36 V, higher than the DC voltage supplied by the fire receiver 11 is used.

The other Zener diode ZD2 is an element that generates a voltage that causes a current to flow and determines that a fire has occurred on the fire receiver 11 side when a fire detector 13 equipped with this element is reverse-connected between the L line and the C line, and an element with a low Zener voltage of several volts is used. Note that the aforementioned Patent Document 1 describes a pair of reverse-connected Zener diodes (Figure 4), but these Zener diodes are both voltage-resistant protection elements with high Zener voltages, and the detector of this embodiment differs from the voltage-resistant protection circuit of the detector of the invention in the cited document 1 in terms of the Zener voltage and function of one of the elements (ZD2).

In addition, in the sensor of this embodiment, the diode D1 connected in series with the sensor internal circuit 32 passes current to operate the sensor internal circuit 32 normally when the sensor is correctly connected between the L line and the C line, but when the sensor is reversely connected between the L line and the C line, it blocks the current from flowing and puts the sensor internal circuit 32 in a non-operating state.

The detector shown in Figure 2(B) has a Zener diode ZD1 and a constant current diode CRD1 connected in series between the L terminal 31A and the C terminal 31B, with their cathode terminals on the L terminal 31A side. The Zener diode ZD1 is a voltage protection element with a high Zener voltage (e.g. 36V). On the other hand, the constant current diode CRD1 is an element that can always pass a constant current even if the applied voltage or load resistance changes, and the pinch-off current (value that results in a constant current) is a value, for example a few mA, at which the receiver can determine that a fire has occurred.

In addition, the sensor of FIG. 2(B), like the sensor of FIG. 2(A), is provided with a backflow prevention diode D1 connected in series with the sensor internal circuit 32 between the L terminal 31A and the C terminal 31B.
2(B), when the sensor is properly connected between the L and C lines, the diode D1 passes current and operates the sensor internal circuit 32 normally, whereas when the sensor is reverse-connected between the L and C lines, the current is prevented from flowing and the sensor internal circuit 32 is put into a non-operating state. Also, when the sensor is reverse-connected, a forward voltage is applied to the constant current diode CRD1 and the Zener diode ZD1, causing a current to flow, which in turn causes a current to flow in the L and C lines, enabling the receiver to determine that a fire has occurred.

2C shows a sensor in which a Zener diode ZD1, a light emitting diode LED1, and a resistor R1 are connected in series between the L terminal 31A and the C terminal 31B, with the cathode terminals of ZD1 and LED1 on the L terminal 31A side. The Zener diode ZD1 is a voltage-resistant protection element having a high Zener voltage (e.g., 36 V).
As in the sensor of FIG. 2A, a diode D1 for preventing backflow is provided between the L terminal 31A and the C terminal 31B and is connected in series with the sensor internal circuit 32.

In the detector of Fig. 2(C), when the detector is reversely connected to the L and C lines, a forward voltage is applied to the light-emitting diode LED1 and the Zener diode ZD1, causing a current to flow, which in turn causes a current to flow to the L and C lines, allowing the receiver to determine that a fire has occurred. In addition, the current flowing through the light-emitting diode LED1 causes it to emit light. Therefore, an operator can visually confirm the emission of light and understand that a reverse connection has occurred. In addition, a forward voltage is applied to the Zener diode ZD1, causing a current to flow, which in turn causes a current to flow to the L and C lines, allowing the receiver to determine that a fire has occurred (reverse connection).
If the housing of the sensor is made of plastic, the light emitting diode LED1 can be mounted close to the wall of the housing, whereby light can pass through the material of the housing and leak out, making it visible. In order to improve the visibility of the light emitting diode LED1, a thin portion or a through hole may be formed in the wall of the housing near the mounting location.

The detector shown in Figure 2(D) is a modified version of the detector in Figure 2(A), in which a light-emitting diode LED1 and resistor R1 are connected in series in parallel with a Zener diode ZD2. The detector in Figure 2(D) has the same function as the detector in Figure 2(A), and when the detector is reverse-connected to the L and C lines, a current flows through the light-emitting diode LED1, causing it to emit light. Therefore, workers can visually confirm the emission of light and know that a reverse connection has occurred. In addition, a forward voltage is applied to the Zener diode ZD1, causing a current to flow, which in turn causes a current to flow through the L and C lines, allowing the receiver to determine that a fire has occurred (reverse connection).

The detector shown in FIG. 2(E) is a modified version of the detector in FIG. 2(B), in which a light-emitting diode LD1 is connected in series between the Zener diode ZD1 and the constant current diode CRD1. The detector in FIG. 2(E) has the same function as the detector in FIG. 2(B), and when the detector is reverse-connected to the L and C lines, a current flows through the light-emitting diode LED1, causing it to emit light. Therefore, workers can visually confirm the emission of light and know that a reverse connection has occurred. In addition, a forward voltage is applied to the Zener diode ZD1, causing a current to flow, which in turn causes a current to flow through the L and C lines, allowing the receiver to determine that a fire has occurred (reverse connection).

Next, we will explain the work of connecting the fire detector 13 of the above embodiment to the L and C wires that constitute the detector circuit laid in the ceiling space or the like in the monitored area, and installing it on the ceiling surface or the like, and how to determine whether it is connected in reverse.
The work of connecting the fire detector 13 to the L line and the C line and installing it is usually performed with the fire receiver 11 switched to a maintenance mode (construction mode) or with the power turned off for the fire receiver 11. The maintenance mode is set by operating a mode switching means provided in the fire receiver 11, and in the maintenance mode, the L line is at ground potential (0 V) like the C line.

In this state, suppose that while a worker is installing multiple detectors in sequence from the side closest to the fire control panel 11 to the side furthest from it, he accidentally connects detector 13B in reverse to wires L and C, as shown in Figure 3. In this case, the worker will not notice that he has connected them in reverse, and so detectors after detector 13B will usually be connected in reverse.
After that, when the installation of all the detectors on all the circuits is completed, switch from the maintenance mode to the regular operation mode, or turn on the power of the fire receiver 11. Then, if there is a detector connected in reverse as in Fig. 3, current flows through the Zener diode ZD2 of the detector connected in reverse in the case of the detector in Fig. 2(A), and through the constant current diode CRD1 of the detector connected in reverse in the case of the detector in Fig. 2(B), so that current flows through the L and C lines that make up the circuit in which the detector connected in reverse is located.

There are two types of fire receivers: one that detects an increase in current to determine whether a fire has occurred, and one that detects a change in voltage to determine whether a fire has occurred. In a system that uses the former type of fire receiver, when the fire receiver 11 detects that the current flowing in from the C line has increased by more than a predetermined value, it determines that a fire has occurred and issues a fire alert. On the other hand, in a system that uses the latter type of fire receiver, when the fire receiver 11 detects that the voltage on the L line has dropped by more than a predetermined value, it determines that a fire has occurred and issues a fire alert (by displaying or outputting a sound).

It is unlikely that a fire has occurred immediately after switching from maintenance mode to actual operation mode, or when the fire receiver 11 is powered on after the installation of the detectors is complete, so when a fire is detected, the fire receiver 11 can determine that there is a detector that is reverse-connected and report this fact. Therefore, a construction supervisor waiting in front of the receiver can contact the worker at the work site by mobile phone to request that the connection be checked, and if a reverse connection is found, it can be corrected. Also, when the fire receiver 11 issues a fire alert, a worker can go to the area to check whether or not there is a fire, and if there is no fire, it can be determined that a detector is reverse-connected and check the connection.

On the other hand, in a fire alarm system using the sensors of Figures 2 (C) to (E) if a sensor is connected in reverse as in Figure 3, the light-emitting diode LED1 inside the sensor lights up immediately after switching from maintenance mode to regular operation mode, or immediately after sensor installation is completed and the fire receiver 11 is powered on, allowing workers to easily determine the presence of a sensor that is connected in reverse and which sensor is connected in reverse. In the case of Figure 3, the reverse connection can be eliminated and the connection can be corrected by finding the sensor that is closest to the fire receiver 11 among the reverse-connected sensors and correcting the connection to the wiring.

As described above, in a fire alarm system using the fire detectors of the above embodiments, even if the L terminal 31A of a detector is mistakenly connected to the C line and the C terminal 31B is mistakenly connected to the L line during the installation work of the detectors, resulting in a reverse connection state of the detectors, it is possible to know that a reverse connection state has occurred in one of the detectors by switching the mode or turning on the power of the fire receiver 11 after installation is completed.

The fire detector of the above embodiment can simplify the circuit configuration compared to a case where a diode bridge circuit is provided at the detector's signal input/output to avoid malfunctions associated with the occurrence of a reverse connection state, and in that case, costs can be kept down. Furthermore, providing a diode bridge circuit reduces the voltage amplitude of the L and C lines, which may reduce the accuracy of fire detection in this operation mode. However, in a fire alarm system using the fire detector of the above embodiment, it is possible to avoid a reduction in the voltage amplitude of the L and C lines, which has the advantage that there is no risk of reducing the accuracy of fire detection in this operation mode.

Although the present invention has been described above based on the embodiments, the present invention is not limited to the above-mentioned embodiments. For example, in the above-mentioned embodiments, the receiver determines the occurrence of a fire based on a change in the applied voltage or the amount of current flowing, but the receiver may be configured to detect reverse connection of a sensor by detecting a short circuit or an overcurrent instead of a fire.
Furthermore, the order of each element such as the Zener diode, constant current diode, light emitting element, resistor, etc. in the embodiments and modified examples of Figures 2(A) to (E) is not limited to that shown in the figures, and they may be connected between the L terminal 31A and the C terminal 31B in a different order.

11 Fire receiver 12A L line (signal line)
12B C line (signal line)
13 Fire detector 14 Termination resistor 31A L terminal 31B C terminal 32 Detector internal circuit ZD1, ZD2 Zener diode CRD1 Constant current diode LED1 Light emitting diode

Claims (5)

A fire detector having a common terminal and a line terminal connected to a common line and a line line constituting a signal line, and receiving power from a fire receiver via the signal line,
Two Zener diodes are connected in series between the common terminal and the line terminal in opposite directions;
A fire detector characterized in that one of the two Zener diodes has a Zener voltage higher than the DC voltage of the power supply, and the other Zener diode has a Zener voltage lower than the DC voltage of the power supply. A fire detector having a common terminal and a line terminal connected to a common line and a line line constituting a signal line, and receiving power from a fire receiver via the signal line,
A fire detector characterized in that a constant current diode, through which a predetermined current flows when a DC voltage of the correct polarity and the opposite polarity from the power source is applied between the common terminal and the line terminal, is connected. The fire detector according to claim 2, characterized in that a Zener diode having a Zener voltage higher than the DC voltage of the power supply is connected in series with the constant current diode in the reverse direction between the line terminal and the common terminal. A fire detector having a common terminal and a line terminal connected to a common line and a line line constituting a signal line, and receiving power from a fire receiver via the signal line,
A fire detector characterized in that an indication means that lights up when a DC voltage of opposite polarity to the correct polarity is applied from the power source and a Zener diode having a Zener voltage higher than the DC voltage of the power source are connected in series between the common terminal and the line terminal. A fire alarm system including the fire detector according to any one of claims 1 to 4 and a fire receiver that notifies the occurrence of a fire when a predetermined voltage signal or current signal is input from the fire detector via the signal line,
The fire receiver includes:
When a voltage signal or a current signal indicating the occurrence of a fire is input from the signal line immediately after power is turned on in a state in which a plurality of the fire detectors are connected to the signal line, the fire occurrence is notified, and
A fire alarm system characterized by determining that the common terminal and line terminal of any of a plurality of fire detectors connected to the signal line are reversely connected to the common line and line line, and notifying of the reverse connection.

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