JPS6026173B2 - Smoke detectors - Google Patents

Description

[Detailed description of the invention] The present invention relates to a photoelectric scattering type smoke detector.

The photoelectric scattering type bonito sensor uses the scattering of light by smoke to detect smoke concentration, and has a measurement darkroom that allows smoke to easily flow in and blocks outside light. A light emitting source, such as a light emitting diode, and a light receiving body, such as a photodiode, are placed at a position that does not directly receive light from the light emitting source but receives scattered light from the smoke when smoke is present, and the smoke concentration is determined by the output of the light receiving body, such as a photodiode. It is configured to sense. In conventional photoelectric smoke detectors, fluctuations in power supply voltage,
Various measures have been taken, such as providing a compensation circuit for changes in ambient temperature and an amplifier circuit for detecting weak scattered light, or enclosing the entire device in a metal shield case. However, it is not possible to compensate for a decrease in the amount of light emitted due to deterioration of the light emitter, or a decrease in the amount of light due to the absorption of light by the dirt layer due to the adhesion of dirt to the surfaces of the light emitter and photoreceptor.

Therefore, calibration and cleaning must be performed periodically, which requires a great deal of effort in automatic fire alarm systems equipped with a large number of sensors. Furthermore, the performance of the sensor deteriorated before the periodic inspection. Since failures cannot be detected, they can cause false alarms and other problems that reduce the reliability of the system as a whole. In addition, there are many problems such as prevention of malfunction due to electrical conduction noise in the smoke detector.
The present invention aims to provide a bonito sensor with high stability and reliability that solves these conventional problems, and its basic configuration and functions are as follows.

The photoelectric scattering light type smoke detector of the present invention is equipped with a light amount compensation control circuit that compensates for changes in light amount due to changes in power supply voltage and ambient temperature, as well as deterioration of the emitter and photoreceptor and dirt on the surface. The structure is such that an output proportional to the smoke concentration can be obtained. Furthermore, by changing the light intensity setting reference value of the light intensity compensation control circuit and programmatically changing the sensitivity of the sensor, it has a check function that automatically checks the function of the sensor using an internal or external signal. Furthermore, it is equipped with a circuit to prevent malfunctions caused by external electrical noise. The first feature of the present invention is that, in addition to the scattered light receiver placed in the measurement dark box at a position that does not directly receive light from the light emitter, a direct light receiver is placed at a position that directly receives light from the light emitter.

Preferably, these two photoreceptors have the same characteristics. Now, if the light intensity of the light emitter decreases due to deterioration of the light emitter, dirt on the surface, etc., or changes due to power supply voltage or temperature, the direct light and scattered light will change at the same rate.
If the dirt on the surfaces of the direct light receiver and the scattered light receiver are the same, the ratio of the outputs of these two light receivers will be proportional only to the smoke density, regardless of the amount of light emitted, temperature changes, and the degree of surface dirt.

There are two ways to compensate for such changes.
The first method is to divide the output of the scattered light photoreceptor by the output of the direct photoreceptor, and is a method using a blitz circuit or an analog calculation circuit. The second method is a method in which the amount of light emitted by the light emitter is controlled by the output of the direct light receptor. A constant amount of received light can be obtained by amplifying the output of the direct photoreceptor, taking the difference from the reference voltage, and feeding this difference back to the power source of the light emitter. The intensity of scattered light is proportional to the intensity of direct light, so when the output of the direct light receiver is constant, the output of the scattered light receiver is determined by keeping the value of the denominator of the division in the first method constant. Similarly, the output of the scattered light receiver is proportional only to the smoke density. The first feature of the present invention is to use the above method to ensure a stable smoke sensing function over a long period of time, and the second feature of the present invention is to check the electrical operation function. That is, the first
When using the above second method for the characteristics of By using this relationship, it is possible to check the operational function of the bonito detector as a whole. Even when there is no smoke, there is a background due to reflections and scattered light from the walls of the dark room, so the value is also multiplied by k, and it is possible to check the operation function in the same way as when there is smoke.
Functional checks may be performed from time to time, and may be performed using an internal timer or an external signal. As a result, whether the scattered light output level is correctly multiplied by k is determined by a comparison circuit inside or outside the sensor. Note that, in realizing the operational function check, it is of course possible to use the above-mentioned first method, which is the first feature. The third feature of the present invention, the malfunction prevention circuit against electrical noise, utilizes the fact that smoke density changes are relatively gradual to determine the output voltage y of the scattered light receiver at a certain time t2, and Output voltage Vt until time t3, which is approximately several tens to several hundreds of rs
The data is constantly compared with the values of IVt2 to t3, and if the value of IVt2 - Vt2 to t3l exceeds the threshold V ratio even for a moment, that data is canceled. This is effective in preventing malfunctions caused by noise in photoelectric smoke detectors that operate in pulse mode.

Next, embodiments of the present invention will be described in detail. FIG. 1 is a diagram showing the overall configuration of a first embodiment of a photoelectric scattering type bonito sensor of the present invention. 1 is a light emitting diode, 2 is a direct light receiving photodiode provided in a position to receive direct light from the light emitting diode 1, 3 is a scattered light receiving photodiode provided in a position not directly receiving light from the light emitting diode 1, and 4 is the above-mentioned. A light shielding plate 5 serves to prevent light from directly entering the scattered light receiving photodiode 3, and an amplifier 5 amplifies the output of the scattered light receiving photodiode 3.

6 is a light amount compensation control circuit for controlling the output of the direct light receiving photodiode 2 to be constant; 7 is a sequence control circuit; 8 is a malfunction prevention circuit; 9 is an output circuit; and 10 is a receiver.

Reference numerals 11, 12, and 13 are control signals sent from the sequence control circuit 7 to the light amount compensation control circuit 6, malfunction prevention circuit 8, and output circuit 9, respectively.

28 is a measurement dark box that allows smoke to easily enter and blocks outside light.

The light emitting diode 1 and the direct light receiving phytodiode 2 in the measurement darkroom 28 are arranged close to each other on the same optical axis.
The output of the photodiode 2 is fed back to the light emitting diode 1 via the light intensity compensation control circuit 6, and the output of the direct light receiving photodiode 2 is controlled to be constant. The amount of light emitted from the light emitting diode 1 is always constant even if

In addition, since the direct light receiving photodiode 2 and the scattered light receiving photodiode 3 are installed close to each other in the same measurement darkroom 28, the degree of surface contamination of both is approximately the same, and the rate of light absorption by the contaminant layer also increases. It's the same. Therefore, if the output of the direct light receiving photodiode 2 is controlled to be constant, the scattered light receiving photodiode 3
The output is independent of the deterioration of the light emitting diode, changes in luminous efficiency due to temperature, dirt on the surface, etc., and is proportional only to the smoke density. FIG. 2 shows a detailed configuration diagram of the light amount compensation control circuit portion.

1 is a light emitting diode, 2 is a direct light receiving photodiode, 3 is a scattered light receiving photodiode, 4 is a light shielding plate, 5 is an amplifier for amplifying the output of the scattered light receiving photodiode 3, and 25 is an output signal thereof. Reference numeral 14 denotes an amplifier for amplifying the output of the direct light receiving photodiode 2.

Note that 22 represents smoke particles, 23 represents direct light, and 24 represents scattered light. 15 is a differential amplifier, 18 is a changeover switch, 19 is a reference voltage for setting the amount of light during normal operation, and 20 is a reference voltage for setting the amount of light when checking the operating function.

21 is an analog switch, 11 is a control signal for the analog switch 21, 16 is a transistor for driving a light emitting diode, and 17 is a power source thereof.

The output of the direct light receiving photodiode 2 which has received the direct light from the light emitting diode 1 is amplified by the amplifier 14, compared with the reference voltage 19 by the multiplex amplifier 15, and the difference is sent to the base of the transistor 16 via the analog switch 21. - A direct light receiving photodiode 2 in which the drive current of the light emitting diode 1 is controlled to change the amount of light emitted, and the difference between the output of the direct optical amplifier 14 and the reference voltage 19 is constant, that is, determined by the value of the reference voltage 19. Feedback is applied so that the amount of received light is obtained.

By using the analog switch 21 and its control signal 11 as intermittent pulses, the circuit can be operated in an intermittent manner, and the light emitting operation can be performed in an intermittent manner. In this case, since the amount of emitted light can be sufficiently reduced using only the energy stored in a large capacity capacitor as the power source 17, the power source capacity can be reduced. Of course, the average power consumption can be reduced by wind. As mentioned above, the light intensity of the direct light is a constant value determined by the reference voltage, so the reference voltage can be changed by 20' to the light intensity setting reference voltage when checking the operation function by switching the switch 18 internally or externally. If the amount of direct light received is set to a certain ratio, for example, twice, the amount of scattered light received at that point will also be doubled. Even when there is no smoke, there is a background due to reflections from the dark room's side surfaces and scattered light, so the relationship is the same as when there is smoke. The timing and control of this operational function check are performed by the sequence control circuit 7, the scattered light output level is determined by a comparator provided in the output circuit 9, and the result is displayed on an indicator light provided in the sensor. Alternatively, it is transmitted to the receiver 10 to check the operational function. In this case, a separate operational function check line may be provided, or an intermittent signal may be used to distinguish it from a normal smoke detection alarm. The output circuit 9 in this case is also controlled by the sequence control circuit 7. In the manner described above, the operational function can be checked with the sensor installed.

Next, the malfunction prevention circuit 8 shown in FIG. 1 will be explained in more detail.

FIG. 3 is a diagram showing the detailed configuration of the malfunction prevention circuit 8;
Figures A to C are diagrams for explaining the operation.

In FIG. 3, 3 rivers are analog memories, 31 is a comparator with a function value, 32 is a latch circuit, 33 is an analog switch, 34 is a write control signal for the analog memory 30,
35 is a control signal for the latch circuit 32, and 36 is a strobe signal.

25 is an input signal, and 37 is an output signal.

In Figs. 4A to 4C, Fig. 4A is normal when there is no harmful noise in the scattered light output, and Fig. 4B is normal. C shows an abnormal case in which harmful noise is superimposed.

Further, Vh is the value of the input signal 25 at time t2, VS
is the value of the input signal 25 from time t to t3. Vt
h is a threshold value determined around the Vh. Next, the operation will be explained. The input signal 25 is the output of the scattered light output amplifier 5, and is a voltage proportional to the smoke concentration. Now, when the value of this input voltage 25 in time law 2 is written to the analog memory 30 by the control signal 34, the analog memory 30
The output of is held at Vh. Next, the subsequent input signal 2
5, that is, the value Vs from time ra to ra, and the value Vh previously held in the analog memory 301 are compared by the comparator 31 from t2 to t3, and the value is If the ratio is IVh-Vsl to V, the latch circuit 32 works to close the analog switch 33 at time t3, and IVh-Vsl>Vth even momentarily during the gap.
Then, the analog switch 33 is activated by the latch 532.
The latch is applied to prevent it from closing. This situation is shown in Figure 4A.
．． B. Shown in C. Therefore, IVh−Vsl−Vth
In the case of IVh-Vsl>Vth, the analog switch 33 closes, so Vh previously held in the analog memory 30 appears at the output terminal 37, and when IVh-Vsl>Vth, the analog switch 33 does not close, so no output is output to the output terminal 37. No signal appears. Further, if necessary, this relationship can be sent as a strobe signal 36 to the next output circuit 9 and used for data confirmation. Note that the control signals 34 and 35 are the control signal 1 from the sequence control circuit 7 in FIG.
Given as 2. Note that since the operational function check and the normal operation operate independently, the operation of the malfunction prevention circuit is not hindered. In other words, the malfunction prevention circuit 8 operates in the same manner as in normal operation even during the operational function check. In addition, in order to perform a highly accurate operational function check in the intermittent pulse operation, it is desirable to perform the check operation immediately after the normal operation, and to perform the operational function check while the smoke density does not substantially change.

The output of the scattered light receiving photodiode 3 subjected to signal processing as described above is outputted to the final output circuit 9 as an analog signal according to the smoke density, an on/off binary signal with a certain smoke density as a threshold value, or a multilevel signal. It is transmitted as a value signal to the receiver 10 to display the smoke concentration or issue an alarm.

In the above embodiment, the light emitting diode is a gallium/phosphorus infrared light emitting diode, the light receiving photodiodes 2 and 3 are planar type silicon photodiodes, the amplifier is a bipolar and CMCS obeamp, and the control circuit is a TTL and CMSIC were used.

The operation was driven by pulses at approximately 4-second intervals, and power was applied intermittently to all circuits that did not require continuous application.

The period of one sensing operation is approximately 1 millisecond, and approximately 5 seconds after power is applied.
When the measured value becomes stable after 00 microseconds have elapsed, that is, at time t2 shown in FIG. After that, measurements were taken at the time. The operational function check is carried out by switching the switch 18 in the sequence control circuit 7 every 5 to 6 hours. It can also be done at any time using a manual push spade switch. When the output is an analog output, the smoke density is 10%/enemy, it is 2V, and the light amount change magnification for the operation function check is set to 2 times. The average power consumption during alarm was about 3 hV. FIG. 6 shows a second embodiment of the invention.

The difference from the first embodiment is that data can be exchanged bidirectionally between the smoke detector and the receiver. 38 is an output circuit that has the function of transmitting data from the dust detector and receiving commands from the receiver, and 39 has the function of receiving data from the smoke detector and transmitting commands to the smoke detector. 40 is a bidirectional communication line connecting the output circuit 38 and the receiver 39, and 26 is a control line between the sequence control circuit 7 and the output circuit 38.

Further, the output circuit 38 has an individual address identification function using pulse codes or tone signals, and the receiver 39
A specific sensor among a larger number of sensors can be called, data collection, and operational function checks can be controlled on the receiver side. The rest of the configuration is the same as the first embodiment and has the same functions.
As described above in detail regarding the embodiments of the present invention,
The photoelectric scattering light type smoke sensor of the present invention can accurately detect smoke density even when there is deterioration of the light emitting body and the light receiving body, changes in ambient temperature, surface dirt, etc.

In addition, it has a function that automatically checks the operating function and prevents malfunctions due to noise, so it can provide highly reliable and stable smoke detection over a long period of time, increasing the reliability of automatic fire alarms that use it. This has many effects, such as being able to significantly reduce the incidence of non-fire alarms.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing a first embodiment of the present invention, FIG. 2 is a block diagram of a light amount compensation control circuit portion of the same embodiment, FIG. 3 is a block diagram of a malfunction prevention circuit of the same embodiment, and FIG. 4A to 4C are diagrams for explaining the operation of the malfunction prevention circuit of the same embodiment, and FIG. 5 is a configuration diagram showing a second embodiment of the present invention. 1... Light emitting diode, 2... Direct light receiving photodiode, 3... Scattered light receiving photodiode, 4... Light shielding plate, 5... Amplifier, 6...Light amount compensation control circuit, 7...
Sequence control circuit, 8... Malfunction prevention circuit,
9...Output circuit, 10...Receiver, 1
4... Amplifier, 15... Differential amplifier,
16...Transistor, 17...Power supply, 1
8...Analog switch, 19,20...
...Reference voltage, 21...Analog switch, 2
2...Smoke, 23...Direct light, 24...
Scattered light, 30...Analog switch, 31...
Comparator, 32... Latch circuit, 33...
・Analog switch, 38...Output circuit, 39...
...Receiver. Figure 1 Figure 2 Figure 3 Figure 4 Figure D5

Claims (1)

[Scope of Claims] 1. A light-emitting body in a dark box that allows smoke to easily enter and blocks outside light, a direct light receiver provided at a position to receive direct light from the light-emitting body, and a direct light receiver provided in a position to receive direct light from the light-emitting body. Instead of receiving direct light, it receives scattered light from incoming smoke. a scattered light photoreceptor, and a light amount compensation control circuit that controls the amount of light emitted from the light emitter so that the output of the direct light photoreceptor is constant; and a light amount setting reference voltage of the light amount compensation control circuit is switched. an operation function confirmation circuit that determines the output of the scattered light photoreceptor; and after once holding the output of the scattered light photoreceptor, the held value is compared with the subsequent output of the scattered light photoreceptor over a predetermined period of time; and a malfunction prevention circuit that determines whether or not the stored signal is within a predetermined value range, and an alarm generation circuit that compares the held signal with a reference value for alarm generation.