JP7841904B2 - fire detector - Google Patents

Description

This invention relates to a fire alarm system, and to a fire alarm receiver and detector used in a fire alarm system.

Fire alarm receivers come in two types: pulsating current and direct current. The receiver extends a localized circuit line to connect detectors, to which one or more detectors are connected. In pulsating current receivers, pulsating current is applied to the localized circuit line, while in direct current receivers, direct current is applied to the localized circuit line. In the direct current type, the receiver and detectors have communication capabilities, sending and receiving various information, which may be used as necessary information for fire response.
While pulsating current (DC) type fire alarms were once dominant, DC type alarms have become the mainstream recently. Some DC type alarms allow the fire alarm receiver and detector to communicate and exchange information, enabling more precise fire alarms, and these have become increasingly common in recent years. However, pulsating current fire alarm receivers still exist and continue to operate. Therefore, suppliers need to provide detectors compatible with pulsating current as needed for maintenance. This means suppliers must offer both pulsating current and DC type detectors, resulting in an increased variety of detector models.

Japanese Patent Application Publication No. 10-188154

As shown in Patent Document 1, there are detectors with communication functions that can communicate with fire alarm receivers. In this case, the fire alarm receiver applies DC current to the district circuit line. When a detector with a communication function is connected to a pulsating-current type fire alarm receiver, the communication function can be disrupted by voltage fluctuations (full-wave or half-wave waveform) of the pulsating current, which can lead to increased current consumption in the detector or cause the detector to detect a communication error and become unable to operate normally.

Therefore, the present invention has been made in view of these points, and aims to enable the installation of communication-enabled detectors in pulsating-current type fire alarm receivers by preventing the system from detecting a communication error or malfunction even when a communication-enabled detector is installed in the receiver.

To achieve the above objective, the fire detector according to claim 1 of the present invention is a fire detector with a communication function connected to a district circuit line extending from a fire receiver, and is characterized in that it has a pulsating current detection circuit for detecting pulsating current , and further has a communication circuit that can exchange information with the fire receiver by communication, and when the pulsating current detection circuit detects that pulsating current is applied to the district circuit line, it stops the communication function of the communication circuit.

A fire detector with the above configuration includes a pulsating current detection circuit. When a pulsating current applied to a local circuit line is detected, the communication function can be shut down. This reduces unnecessary operation and thus lowers the power consumption of the fire detector.

The communication circuit according to claim 2 is characterized in that it stops detecting communication abnormalities when the communication function is stopped.

With a sensor having the configuration described above, even when connected to a pulsating current type receiver, it will not detect communication abnormalities, thus preventing the output of unnecessary alarms.

The pulsating current detection circuit according to claim 3 is characterized in that it determines that a pulsating current is being applied to the district circuit line when it detects that the voltage applied to the district circuit line falls below a predetermined threshold at predetermined time intervals.

The above configuration allows for the detection of pulsating current using a simple method, resulting in the ability to create a low-cost pulsating current detection circuit.

The pulsating current detection circuit according to claim 4 is characterized in that it determines that a pulsating current is being applied to the district circuit line when it detects a communication abnormality a predetermined number of times consecutively.

The above configuration allows for the detection of pulsating current using a simple method, resulting in the ability to create a low-cost pulsating current detection circuit.

According to the present invention, it becomes possible to use a sensor with a communication function in a pulsating current type receiver, and since sensors can be shared, the number of types of sensors can be reduced, thereby lowering the cost of sensors. Furthermore, the number of types of sensors to be selected is reduced during equipment design and installation, thus reducing the effort required for sensor selection.
Furthermore, it can prevent false detections and false alarms of communication anomalies caused by pulsating current, and reduce the power consumption of the sensor.

This diagram shows an example configuration of the fire alarm system S. This figure shows the pulsating current waveform and DC waveform applied to the district circuit line. This is a block diagram showing the configuration of a pulsating-type fire alarm receiver and detector. This is a block diagram showing the configuration of a DC type fire alarm receiver and a detector with communication function. This is a block diagram showing the configuration of a pulsating current type fire alarm receiver and a detector with communication capabilities.

Figure 1 shows an example configuration of a fire alarm system S. The fire alarm system S comprises a fire alarm receiver 1 and multiple detectors 3. The fire alarm receiver 1 is connected to multiple zone circuits 2, which in turn connect to the multiple detectors 3. The zone circuits 2 are external wiring responsible for communication signals and power supply between the fire alarm receiver 1 and the detectors 3. The number of detectors 3 that can be connected to a pair of zone circuits 2 is determined by the system, and multiple zone circuits 2 may be used as needed. Figure 1 shows a case where multiple zone circuits 2-1, 2-2, and 2-n are used. The detectors 3 detect smoke and heat generated by the fire as environmental information and generate environmental data.

The district circuit line 2 connecting the fire alarm receiver 1 and the detector 3 serves both as the detector's power source and communication line. To simplify the power supply circuit, the fire alarm receiver 1 may not have a smoothing circuit and may apply pulsating current to the district circuit line 2. This is referred to here as the pulsating current type. In this case, the connected detector 3 requires a smoothing circuit at the input of the district circuit line 2 to convert the pulsating current to DC, which inevitably increases costs.
Using pulsating current in district circuit line 2 makes communication difficult, so it is rarely used in modern systems that require communication. However, there are still many pulsating current type systems in operation.
[Explanation of Figure 2(a)]

This diagram schematically represents the pulsating waveform of full-wave rectification. From left to right in Figure 2(a), the waveforms represent the fire monitoring period, detector activation (fire detection), recovery pulse, and fire monitoring period (restart). When fire monitoring is performed using pulsating current, detector 3 detects a fire and activates, causing the impedance inside the detector to decrease to an L level. At this L level, the voltage is approximately 1-6V, depending on the characteristics of the switching element inside the detector. When the area circuit line 2 becomes L due to detector activation (fire detection), receiver 1 detects this and issues a fire indicator or alarm. The detector maintains its L level, indicating a fire condition.

After the presence or absence of a fire is confirmed, the operator's recovery operation causes the fire alarm receiver 1 to send a recovery pulse (which stops the power supply to the area circuit line for a predetermined period of time, bringing it to 0V), releasing the self-holding of the detector 3, and the detector 3 returns to the monitoring state. When the detector 3 is self-holding, it releases the self-holding if it detects a recovery pulse.
[Explanation of Figure 2(b)]

This system uses a fire alarm receiver 1 to apply direct current to the district circuit line 2.

This diagram schematically represents the waveform of the rated voltage of 24V DC. From left to right in Figure 2(b), the waveforms represent the fire monitoring period, the detector activation/communication period, the recovery pulse, and the fire monitoring period (restart).

When the detector is activated, the impedance inside the detector decreases to an L level. At this L level, the voltage is approximately 1V to 6V, depending on the characteristics of the switching element inside the detector. When the activation of detector 3 (fire detection) causes the area circuit line 2 to become L, the fire receiver 1 detects this and issues a fire indicator or alarm. After the presence or absence of a fire is confirmed, the operator can perform a recovery operation to send a recovery pulse (which cuts the power supply to the area circuit line for a predetermined time, bringing it to 0V), releasing the self-holding mechanism of detector 3, and detector 3 returns to the monitoring state.

Here, the difference from Figure 2(a) is that, in addition to the difference between pulsating current and direct current, communication takes place during the communication period when the detector is activated. (Only when using a detector and receiver with communication functions) During this period, the fire alarm receiver 1 exchanges fire information and individual information of detector 3. In this example, the communication is shown using pulse waveforms. When detector 3 is self-holding, if the area circuit line 2 becomes 0V due to a reset operation of the fire alarm receiver 1, the detector releases its fire self-hold.

When using a sensor with communication capabilities and a receiver with communication capabilities, the sensor may receive a recovery notification via communication, and at this time, it may release its self-holding mechanism.
[Explanation of Figure 3]

This is a block diagram of a pulsating-current type fire alarm receiver 1 and a pulsating-current type detector 3 using full-wave rectification. The power supply circuit 12 of the fire alarm receiver 1 consists only of a full-wave rectification circuit and does not have a smoothing circuit. Therefore, the voltage waveform generated in the connected area circuit line 2 is a pulsating current with a series of peak-shaped waveforms as shown in Figure 2(a). The pulsating-current type detector 3 is also connected to the area circuit line 2.
[Block diagram of the fire alarm receiver (Figure 3, left side)]

The control circuit 13 is a central circuit that receives and receives information from the various circuits described later, makes decisions, and issues operation instructions.
The fire signal determination circuit 14 is as follows: When the detector 3 detects a fire and turns on the switching circuit 26, the impedance of the zone circuit line 2 drops significantly. A current limiting circuit 11 is provided to protect against damage to the zone circuit line 2 of the fire receiver 1, the switching element of the detector 3, and the power supply circuit 12 of the fire receiver 1, which may occur due to the large current flow caused by the impedance drop. The current limiting value varies depending on the model of the fire receiver 1, but it is generally limited to around 50mA to 100mA.

The fire signal determination circuit 14 monitors the impedance of the district circuit line 2 and determines that the detector 3 is sending a fire signal when it reaches a predetermined value. Although not shown in the diagram, a terminator is connected to the final end of the district circuit line 2 to monitor for disconnections in the district circuit line 2. The fire signal determination circuit 14 also monitors the current passing through the terminator and detects disconnections in the district circuit line 3.

When the fire signal determination circuit 14 determines that there is a fire, the control circuit 13 instructs the alarm circuit 16 and the operation/display circuit 17 to perform actions such as alarm, display, interlocking (not shown), and transmission.
The alarm circuit 16 performs alarm actions corresponding to the fire, such as sounding a main audible alarm or a district bell, according to instructions from the control circuit 13.
The operation and display circuit 17, in accordance with the instructions of the control circuit 13, displays information on the panel of the fire alarm receiver 1 corresponding to the fire, and also transmits the operation details of the fire alarm receiver 1's control unit to the control circuit 13.
When the operation/display circuit 17 receives a recovery operation from the operation unit of the fire alarm receiver 1, the control circuit 13 activates the recovery pulse generation circuit 15 and sends a recovery pulse to the zone circuit line 2, setting the zone circuit line 2 to 0V for a predetermined time. When the zone circuit line 2 is controlled to 0V, the self-holding of the switching self-holding circuit 26 of the detector 3 is released.
[Block diagram of the sensor (right side of Figure 3)]

To obtain power from the district circuit line 2, the pulsating current is smoothed by the smoothing circuit 22, and then converted to the required voltage inside the sensor by the constant voltage circuit 23 and supplied. In this example, a reverse current prevention circuit 21 is provided to ensure efficient operation of the smoothing circuit 22 and to prevent its influence from being transmitted to the district circuit line, thus separating the smoothing circuit 22 from the district circuit line 2.

The fire detection circuit 25 detects the presence and amount of fire phenomena such as smoke, heat, and flames, and sends fire information to the control circuit 24 if it exceeds a predetermined value.

When the control circuit 24 detects fire information, it activates the switching circuit 26 to lower the impedance of the district circuit line 2 and cause it to self-hold. Due to the impedance reduction, the district circuit line 2 becomes low (L), and a fire signal is sent to the fire receiver 1.
[Explanation of Figure 4]

Figure 4 is a block diagram of a DC-type fire alarm receiver 1 and a DC-type detector 3 (with communication function). The power supply circuit 12 of the fire alarm receiver 1 is equipped with a DC power supply circuit that can stably supply DC. Therefore, the voltage waveform generated in the connected area circuit line 2 is the DC waveform shown in Figure 2(b). The area circuit line 2 is also connected to the DC-type detector 3 (with communication function). The fact that the fire alarm receiver 1 and detector 3 have a communication circuit is a major difference from the pulsating current type.
[Block diagram of the receiver (Figure 4, left side)]

I will only explain the points that differ significantly from the pulsating flow type.
The power supply circuit 12 is a circuit that can output a stable DC current, and this stable DC current is applied to the district circuit line 2. A communication circuit 18 is also installed to receive signals from the district circuit line 2, allowing for detailed fire information to be obtained when the detector 3 is sending out a fire signal. The functions of the other circuits are the same as those of the pulsating current type.
[Block diagram of the sensor (right side of Figure 4)]

Similar to the fire alarm receiver 1 described above, only the points that differ significantly from the pulsating current type will be explained.
Since DC is applied to the district circuit line 2, a smoothing circuit is not required in the detector's power supply circuit, and it only has a constant voltage circuit 31 that supplies the necessary voltage. Furthermore, it has a communication circuit 35 to communicate with the fire alarm receiver 1 to transmit and receive fire information. The communication circuit 35 starts communication when it detects a communication pulse. Through communication, it transmits fire information, including the unique information of the detector 3, to the fire alarm receiver 1. Also, if it detects an abnormality in the communication waveform or if the communication procedure is not followed, it stores the abnormality information internally as a communication abnormality and sends the stored abnormality information to the fire alarm receiver 1 when communication is resumed.

Furthermore, in the case of a sensor with a self-diagnostic function, the self-diagnostic results can be transmitted to the receiver 1 via the communication function. The communication protocol will not be discussed here.
The functions of the other circuits are the same as those of the pulsating current type.

[Examples]
[Explanation of Figure 5]
Figure 5 is a block diagram representing an embodiment of the present invention.
[Block diagram of the receiver (Figure 5, left side)]
The fire alarm receiver 1 is the same as the pulsating current type shown in Figure 3. The difference here lies in the internal configuration of the connected detector.
[Block diagram of the sensor (right side of Figure 5)]

In addition to the configuration of the detector 3 in the DC type shown in Figure 4, a pulsating current detection circuit 36 is added. As shown in Figure 2(a), in Japan, in the case of pulsating current, points where the voltage becomes 0V appear periodically, approximately every 10ms for a 50Hz AC input and approximately every 8.3ms for a 60Hz AC input. The pulsating current detection circuit 36 constantly monitors the district circuit line 2, and when it detects the aforementioned pattern, it determines that it is a pulsating current and sends that information to the control circuit 32. When the control circuit 32 receives information that it has detected the pulsating current, the control circuit 32 recognizes that it is connected to the pulsating current type fire alarm receiver 1. From this point onward, the communication circuit 35 is turned OFF, and the communication circuit 35 enters communication OFF mode. While operating in communication OFF mode, it does not perform normal district circuit line communication monitoring or fire information communication, and since unnecessary communication circuit activation is eliminated, current consumption is reduced.

Furthermore, in the case of a detector with a self-diagnosis function, the self-diagnosis result can be transmitted to the fire alarm receiver 1 via the communication function. However, when the detector recognizes that it is connected to a pulsating-current type fire alarm receiver 1, it will also stop transmitting the self-diagnosis result.

As mentioned above, the method for detecting pulsating current involves detecting points where the voltage becomes 0V at regular intervals. However, detecting a positive voltage pulsating sinusoidal waveform is also an option.

Furthermore, if a communication anomaly is detected a predetermined number of times, it may be determined to be a communication anomaly caused by pulsating current, and this can be treated as pulsating current detection.

Although the present invention has been described above using embodiments, the technical scope of the present invention is not limited to the scope described in the above embodiments, and various modifications and changes are possible within the scope of its gist. For example, all or part of the device can be configured by functionally or physically distributing and integrating them in any unit. Furthermore, new embodiments resulting from any combination of multiple embodiments are also included in the embodiments of the present invention. The effects of the new embodiments resulting from the combinations are combined with the effects of the original embodiments.

S Fire alarm system 1 Fire receiver 2, 2-1, 2-2, 2-n District circuit 3 Detector (smoke or heat)
11 Current limiting circuit 12 Power supply circuit 13 Control circuit 14 Fire signal judgment circuit 15 Recovery pulse generation circuit 16 Alarm circuit 17 Operation/display circuit 18 Communication circuit 21 Reverse current prevention circuit 22 Smoothing circuit 23 Constant voltage circuit 24 Control circuit 25 Fire detection circuit 26 Switching self-holding circuit 31 Constant voltage circuit 32 Control circuit 33 Fire detection circuit 34 Switching self-holding circuit 35 Communication circuit 36 Pulsating current detection circuit L Low level

Claims (4)

A fire detector with a communication function connected to a district circuit line extending from a fire alarm receiver, comprising a pulsating current detection circuit for detecting pulsating current , and further comprising a communication circuit capable of exchanging information with the fire alarm receiver, wherein the communication function of the communication circuit is stopped when the pulsating current detection circuit detects that pulsating current is being applied to the district circuit line. The fire detector according to claim 1, characterized in that the communication circuit stops detecting communication abnormalities when the communication function is stopped. The fire detector according to claim 1 or 2, characterized in that the pulsating current detection circuit determines that a pulsating current is being applied to the district circuit line when it detects that the voltage applied to the district circuit line falls below a predetermined threshold at predetermined time intervals. The fire detector according to claim 1 or 2, characterized in that the pulsating current detection circuit determines that a pulsating current is being applied to the district circuit line when it detects a communication abnormality a predetermined number of times consecutively.