JPH0439716B2 - - Google Patents

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention is an analog fire detection system that detects in an analog manner the amount of change in physical phenomena such as smoke and temperature generated due to a fire by intermittent driving. Concerning vessels.

(Prior art) Conventionally, in the case of photoelectric smoke detectors, etc., the detector itself has a fire determination function, and when the detected smoke concentration, etc. reaches a preset threshold, the signal line from the receiver This is a so-called on-off type fire detector that short-circuits the detector to a low impedance and sends an alarm current to the receiver.

However, with on/off type fire detectors, fire detection is based on a fixed threshold value, making it difficult to simultaneously satisfy two contradictory conditions: early detection of fire and prevention of false alarms. Therefore, in recent years, analog fire detection systems have been developed, in which the receiver side has a fire judgment function, and the fire detector detects physical changes in fire phenomena such as smoke concentration in an analog manner and sends it to the receiver. A fire alarm system using a fire alarm is being considered.

On the other hand, similar to conventional on/off type smoke detectors, analog fire detectors detect smoke concentration intermittently and send it to the receiver in order to reduce detector current consumption. There is a need to.

(Problem to be solved by the invention) However, when an analog fire detector is driven intermittently, the light emitting period is extremely short, approximately 0.2 ms, so even if the received light output is sent directly to the receiver, the receiver It is difficult for the receiver to judge reception.

Therefore, it is conceivable to make the light emitting period longer than the time at which reception can be determined on the receiver side, but if the light emitting period is made longer, the original purpose of reducing current consumption is lost.

Another problem with intermittent drive is that
Since the configuration is such that power is intermittently supplied to the light receiving circuit side in synchronization with the light emission drive, there is a relatively large amount of noise mixed into the light reception output corresponding to the initial stage of light emission, making it difficult to accurately determine the accuracy on the receiver side. In order to determine a fire, it is desirable to transmit a signal that reliably removes noise components at the initial stage of light reception.

(Means for Solving the Problems) The present invention has been made in view of these conventional problems, and allows reliable reception judgment on the receiver side without elongating the light emitting period, and also enables intermittent An object of the present invention is to provide an analog fire detector that removes noise mixed into a light reception signal in the initial stage of driving.

In order to achieve this object, the present invention is based on pulse width conversion of the amount of change in a physical phenomenon associated with the occurrence of a fire such as smoke concentration detected intermittently, that is, the detected analog amount, and further pulse width conversion. The detected pulse signal is compared with a reference pulse signal with a constant pulse width to detect the pulse difference between the two pulse signals, and by detecting this pulse difference, noise components included in the initial stage of the received light signal are removed, and finally detected. A signal corresponding to the pulse difference is held and output.

(Embodiment) FIG. 1 is a circuit block diagram showing an embodiment of the present invention.

First, the configuration will be described. Reference numeral 1 denotes a receiver, and one or more analog fire detectors 4 of the present invention are connected between a power signal line 2 and a common line 3 led out from the receiver 1.

The receiver 1 is provided with a receiving section 5, a processing section 6, and a call control section 7, and the receiving section 5 is connected to both ends of a current detection resistor _R0 provided on the common line 3 side, and is connected to an analog fire detector. The analog fire detection signal is received by converting the detection current sent from 4 into a voltage, and in the receiving part 5, the analog detection voltage is converted into a digital signal for fire judgment processing by a processing part 6 using a microcomputer or the like. is converting.
The processing unit 6 determines a fire by predetermined program control based on the digitally converted fire detection signal from the receiving unit 5, and when it determines that there is a fire, it causes an alarm means (not shown) to issue a fire alarm, and also provides evacuation guidance and Furthermore, it controls disaster prevention equipment such as fire doors and smoke prevention doors. The call control unit 7 performs call control (polling) to sequentially call a plurality of analog fire detectors 4 connected to the receiver 1 and return a fire detection signal. A method of calling by sending an assigned address code for each call, or a method of outputting a predetermined clock pulse and, when a predetermined clock pulse count value is obtained on the sensor side, it is determined that the call is its own and a signal is sent back. Any appropriate paging method may be used.

Next, the configuration of the analog fire detector 4 will be explained.

In the analog fire detector 4, 8 is a transmission control circuit that determines a call from the receiver 1 and sets a response time for returning a detector detection signal to the receiver when determining its own call. A response time setting pulse P1 and a light emission drive pulse P2 are output in synchronization with the response time setting pulse P1. The light emitting drive pulse P2 of the transmission control circuit 1 is applied to the light emitting element 9 via the current limiting resistor R1, and the light emitting element 9 is driven to emit light for a fixed period determined by the light emitting drive pulse P2. Further, the light emitting element 9 is installed in a smoke detection chamber inside the sensor housing (not shown), and a light receiving element 10 is installed at a position where the light from the light emitting element 9 does not directly enter.
Scattered light due to the smoke from the light enters. Of course, the light emitting element 9 and the light receiving element 10 may be made to face each other, and the light attenuated by smoke may be incident on the light receiving element 10.

The light receiving element 10 is connected in series with a load resistor R2,
A constant voltage circuit 11 is included in the light receiving circuit of this light receiving element 10.
A more constant voltage is applied, and the light receiving element 10 receives scattered light incident thereon in accordance with the smoke density, passes a light receiving current to the load resistor R2, and generates a signal voltage in accordance with the smoke density across the load resistor R2. The light reception output appearing as a signal voltage of the load resistor R2 is input to the pulse width conversion circuit 12, and is converted into a pulse width corresponding to the signal level of the light reception signal. The converted pulse P3 outputted from the pulse width conversion circuit 12 is transferred to the transistor 13.
The emitter of this transistor 13 is connected to the output of a reference pulse generating circuit 14. The reference pulse generation circuit 14 is the transmission control circuit 8
In response to the response time setting pulse P1, a reference pulse P4 of a certain time width is generated, and while the reference pulse P4 at H level is output, the transistor 1
3 is kept in the cut-off state, and the pulse width conversion circuit 1
Transistor 13 by conversion pulse output P3 of 2
Switching operation is prohibited.

This transistor 13 is connected to the pulse width conversion circuit 12.
It has a function as a pulse difference detection circuit that detects the difference in pulse width between the output pulse P3 obtained in the above and the reference pulse P4 from the reference pulse generation circuit 14.

The collector output of the transistor 13, which functions as a pulse difference detection circuit, is connected to the inverter 1.
5 and is inverted by resistor R3 through diode D1.
The capacitor C is charged with a signal voltage corresponding to the pulse width of the pulse signal P5 outputted from the inverter 15, and the charging voltage of the capacitor C is the same as that of the FET1.
6 gates are given. The gate of FET16 receives a prescribed bias through diode D2, and generates an output voltage in drain resistor R4 according to the charging voltage of capacitor C, and the output of FET16 is given to output circuit 17 provided at the sensor input stage. There is. The output circuit 17 is driven at a predetermined timing within the response time by the transmission control circuit 8,
A signal current corresponding to the output voltage of the FET 16 is passed between the power supply signal line 2 and the common line 3 from the receiver 1, and the fire detection signal detected analogously to the receiver 1, that is, a signal current corresponding to the smoke density. Send out.

Next, the operation of the embodiment shown in FIG. 1 will be explained with reference to the timing chart shown in FIG.

First, at time t1, when the transmission control circuit 8 determines that there is a call from the receiver, a response time setting pulse P1 corresponding to time T1 and a light emission driving pulse P corresponding to time T2 are sent.
Outputs 2. Here, response time setting pulse P1
The pulse width T1 is, for example, several milliseconds, whereas the pulse width T2 of the light emission driving pulse P2 is sufficiently short, about 0.2 milliseconds. As described above, assuming that the smoke density at time t1 when the response time setting pulse P1 and the light emitting drive pulse P2 are outputted is the smoke density in the steady monitoring state where the smoke density is approximately zero, the light emitting element 9 is affected by the light emitting drive pulse P2. Scattered light that is constantly obtained when the smoke concentration is approximately zero enters the light receiving element 10 during light emission driving, and in response to this light reception output, the pulse width conversion circuit 12 converts the pulse width T3 that is fixedly determined in the steady state. Produces a pulse width conversion output P3.

On the other hand, in response to the response time setting pulse P1, the reference pulse generation circuit 14 generates a reference pulse P with a pulse width T4.
4, and the pulse width T4 of this reference pulse P4 is equal to the pulse width conversion output P3 in the steady state.
The pulse width is set to be shorter than the pulse width T3 by ΔT ₀ .

Therefore, even if the pulse width conversion circuit 12 outputs the converted pulse P3, the transistor 13 remains in the cut-off state during the P4 time period during which the reference pulse P4 is generated, and after the T4 time elapses, the reference pulse P3 is output.
4 disappears, the output P3 of the pulse width conversion circuit 12
The transistor 13 switches based on
As a result, the transistor 13 switches during the pulse width difference between the conversion pulse P3 of the pulse width conversion circuit 12 and the reference pulse P4, that is, the pulse difference given by ΔT ₀ =T3−T4, and as a result, the inverter 15 A pulse output P5 having a time width ΔT ₀ corresponding to the pulse difference that the transistor 13 is switching is obtained. This inverter 15
The capacitor C is charged via the resistor R3 by the pulse output P5 of the inverter, and a charging voltage V ₀ corresponding to the pulse width ΔT ₀ of the inverter output pulse P5 is obtained. The signal is held and output to the output circuit 17.

Therefore, the output circuit 17 operates in response to a sending pulse given from the transmission control circuit 8 at a predetermined timing within the response time, and outputs a signal current according to the hold output from the FET 16, that is, the charging voltage V ₀ of the capacitor C. is sent to receiver 1.

Here, the signal current by the output circuit 17 is set to 4~
In the case of 20 mA, in the steady monitoring state where the smoke concentration is approximately zero at time t1 in FIG. 2, a signal current of 4 mA indicating that the smoke concentration is zero is sent to the receiver, and this signal current Therefore, the relationship between the detected pulse difference in the transistor 13, that is, the output pulse width ΔT of the inverter 15, and the output current is as shown in the graph of FIG.

Referring again to FIG. 2, at time t2, when a certain period _T0 has elapsed from time t1, the transmission control circuit 18 again determines that the receiver 1 has been called, and as before, sends the response time setting pulse P1 and the light emission. A drive pulse P2 is output.

For example, if a certain amount of smoke is flowing into the sensor due to a fire outbreak at time t2, the increased smoke concentration will increase the amount of light scattered by the smoke toward the light-receiving element 10, and the light-receiving voltage of the load resistor R2 will increase. As a result, the pulse width conversion circuit 12 generates a pulse width conversion output P3 which is the pulse width ΔT corresponding to the increase in the received light output in accordance with the increase in smoke density to the steady pulse width T3. On the other hand, the reference pulse P4 that keeps the transistor 13 in the cut-off state
Since has a constant pulse width T4, the transistor 13 switches for a change ΔT corresponding to the increase in smoke concentration, and the output pulse P5 of the inverter 15
A pulse with a time width of the change ΔT from the steady monitoring state is obtained, the capacitor C is charged over this ΔT, a signal voltage V corresponding to the increase in smoke concentration is obtained in the capacitor C, and the response is During the response pulse T1 based on the time setting pulse P1, FET1
Hold output is performed at 6. The output circuit 17 outputs a signal from 4 to 4 according to the capacitor charging voltage V at a predetermined timing.
A signal current within the range of 20 mA is sent to the receiver 1.

In this way, in the embodiment shown in FIG.
Receiver 1 with hold output by FET16
It is possible to secure a sufficient signal output period necessary for reception discrimination on the side, and there is no need to lengthen the light emission period by the light emission drive pulse P2, so the current consumption can be reduced by intermittent driving of the sensor. .

On the other hand, the pulse width conversion circuit 12 that converts the received light output into a pulse width is supplied with current by the light emission drive pulse P2 from the transmission control circuit 8, and therefore the power supply is unstable at the initial stage of intermittent drive. The output pulse P3 of the pulse width conversion circuit from
It becomes easy for noise to get mixed into the image.

However, in the embodiment shown in FIG. 1, by detecting the difference in pulse width between the reference pulse P2 and the pulse width converted output P2 in the transistor 13, the pulse width converted output P3, which is the initial part of light emission drive, is detected.
is removed by the reference pulse P4, and the output P5 of the inverter 15, which is the pulse wave detection output, does not include the signal component at the initial stage of light emission drive. Therefore, it is possible to ensure that fluctuations in the capacitor charging voltage due to the contamination of noise components are prevented. can be prevented.

Figure 4 shows the pulse width conversion output P3 and the reference pulse P.
1 is a timing chart showing another embodiment for calculating the pulse difference between the second pulse and the second pulse.
As shown in the timing chart in the figure, we have taken as an example a case where there is a proportional relationship in which the time width ΔT of the pulse signal that provides the pulse difference given by the inverter output P5 also increases as the smoke density increases. The embodiment is characterized in that when the pulse width of the pulse width conversion output P3 increases due to an increase in smoke density, the pulse width ΔT of the inverter output P5 that provides the detected pulse difference becomes shorter. The connections of the pulse width conversion output P3 and the reference pulse P4 input to the pulse width converter 13 are switched.

That is, in the embodiment shown in the timing chart of FIG. 4, the pulse width conversion output P corresponding to the smoke concentration of approximately zero in the steady monitoring state at time t1.
The pulse width T4 of the reference pulse P4 is made larger than the pulse width T3 of No. 3, so that the inverter output P5 that provides the detected pulse difference in the steady monitoring state has a pulse width ΔT ₀ .

With such a setting of the reference pulse P4, when the pulse width conversion output P3 increases in accordance with the increase in smoke density by ΔT indicated by the diagonal line at time t2 when the smoke density increases due to the occurrence of a fire, the reference pulse P4
Since the pulse width of T4 is constant, the pulse width of the inverter output P5 that provides the detected pulse difference changes so that the pulse width becomes shorter in accordance with the increase ΔT in the pulse width of the pulse conversion output P3.

The output current setting for the inverter output T5 is such that the output current is 4 mA at the maximum pulse width ΔT ₀ in the steady monitoring state at time t1, as shown in FIG.
The output current 4 is increased as the pulse width at the inverter output P5 decreases as the smoke density increases.
Configure to increase in the range of ~20mA.

In the case of Fig. 4 as well, the pulse width conversion output P3, which is based on the light reception output at the initial stage of intermittent driving in which noise components are mixed, is completely removed from the pulse difference detection output given by the inverter output P5. , it is possible to send a signal current according to the smoke density to the receiver without being affected by noise generation in the initial stage of intermittent driving.

Although the above-mentioned embodiment takes as an example a photoelectric smoke detector that detects smoke concentration, the present invention is not limited to this, and the present invention is not limited to this, but can also be applied to other changes in physical phenomena associated with fire, such as temperature. The present invention can be applied as is to fire detectors that use an intermittent drive method that detects CO gas concentration, etc., in an analog manner.

(Effects of the Invention) As explained above, according to the present invention, it is basically based on pulse width conversion of the amount of change in a physical phenomenon associated with a fire such as smoke concentration detected intermittently, that is, the detected analog amount. Furthermore, the pulse signal whose pulse width has been converted is compared with a reference pulse signal of a constant pulse width to detect the pulse difference between the two pulse signals, and finally a signal corresponding to the detected pulse difference is held and output, which enables intermittent driving. Even if the light emitting period is extremely short, the fire detection signal can be sent to the receiver over a period in which reception can be determined by the hold output after pulse width conversion. The current consumption due to driving can be sufficiently reduced.

In addition, it converts the detected analog amount into a pulse width, compares the pulse signal converted to pulse width with a constant reference pulse, detects the difference in pulse width between both pulse signals, and holds the signal according to this detected pulse difference. Therefore, by detecting the pulse difference, it is possible to completely remove noise components included in the light reception output at the initial stage of intermittent drive, and even with intermittent drive, an analog fire detection signal with a high S/N ratio can be generated. The analog detection signal can be sent to a receiver, and the receiver can receive and determine the reception of highly accurate analog detection signals, thereby making it possible to make accurate fire judgments.

[Brief explanation of drawings]

FIG. 1 is a circuit block diagram showing an embodiment of the present invention, FIG. 2 is a timing chart showing the operation of the embodiment of FIG. 1, and FIG. 3 is a diagram showing the detected pulse difference in the embodiment of FIG. A graph showing the relationship between the output currents, FIG. 4 is a timing chart showing pulse difference detection according to another embodiment of the present invention, and FIG. 5 shows the relationship between the output current and the pulse difference detection in FIG. 4. FIG. 1...Receiver, 2...Power signal line, 3...
Common line, 4... Analog fire detector, 5...
Receiving unit, 6... Processing unit, 7... Call control unit, 8...
...Transmission control circuit, 9... Light emitting element, 10... Light receiving element, 11... Constant voltage circuit, 12... Pulse width conversion circuit, 13... Transistor, 14... Reference pulse generation circuit, 15... Inverter, 16...
FET, 17...output circuit.

Claims (1)

[Claims] 1. A control circuit that intermittently outputs a drive signal, and a drive signal from the control circuit that intermittently detects the amount of change in surrounding physical phenomena due to the occurrence of a fire, and detects the amount of change. a detection circuit that outputs an analog signal according to the signal level; a pulse width conversion circuit that converts the analog signal output from the detection circuit into a pulse signal with a width corresponding to the signal level and outputs the signal; and simultaneously outputs the drive signal. A reference pulse generation circuit that generates a reference pulse signal of a certain time width to start, and an output pulse signal of the pulse width conversion circuit and a reference pulse signal of the reference pulse generation circuit are compared, and a difference in pulse width between the two pulse signals is determined. A hold circuit that holds and outputs a pulse signal having a time width corresponding to the pulse difference detected by the pulse difference detection circuit; An analog fire detector characterized by comprising: an output circuit that sends a signal to a receiver;