JPS6012238Y2 - Transmitted light smoke detector - Google Patents

Description

[Detailed explanation of the idea] The present invention relates to a transmitted light type smoke detector.

In general, transmitted light type smoke detectors measure the amount of transmitted light, and when the transmitted light decreases as the smoke density increases as the fire progresses, and the transmitted light falls below a certain set value, an alarm is issued. It is being organized.

However, as shown in Fig. 1, in this type of smoke detector, there is a warning area formed by the emitter 1 and the receiver 2 that receives the light, that is, the smoke measurement space, for maintenance and inspection purposes. There are many people coming and going, and obstacles B such as people's hands or ladders may block the transmitted light. In such cases, the smoke detector may activate and issue an alarm even though there is no fire in the first place. There is a problem with giving false alarms.

The present invention was proposed in view of the above points, and uses the difference in the rate of attenuation of transmitted light depending on the smoke concentration to determine whether the smoke detector is operating due to fire smoke, or whether it is caused by a person or someone carrying it. It is determined whether the cause is an obstruction, etc., and in the latter case, a separate alarm from the fire alarm is issued, making it possible to eliminate the source of false alarms such as obstructions, and prevent the occurrence of false alarms. It is an object of the present invention to provide a transmitted light type smoke detector.

Embodiments of the present invention will be described below with reference to the drawings.

The speed of light attenuation when the measurement space is blocked by people or objects held by people is greater than the maximum speed of light attenuation due to smoke from a fire.

FIG. 2 shows this state.

That is, FIG. 2 shows the output of the light receiver of the transmitted light type smoke sensor, where the horizontal axis represents time t1 and the vertical axis represents transmittance (a function of output voltage).

As is clear from this figure, when there is no smoke at all, the transmittance of transmitted light is 100% regardless of time, as shown in C.

On the other hand, when smoke is generated rapidly, such as in a smoke-igniting fire, the output becomes slope A. In this case, slope A is the maximum rate of increase in smoke concentration (e.g. 10%/m/2 to 3sec).
c).

In addition, slope B is a fire that smolders for a long time or once starts to heat up, such as a smoldering fire, and is assumed to be the minimum rate of rise in smoke concentration (for example, 10%/m/day).

Therefore, the curve of change in transmittance due to changes in smoke concentration during a fire can be limited to being within the area surrounded by slopes A and B, and the change curve with a slope within this fire area is It is only necessary to activate the smoke detector and issue an alarm only when smoke occurs.

Also, when a change occurs faster than A (within r=.),
The book determines that the transmitted light is blocked by a person or an object held by the person, and sounds a buzzer etc. from the vicinity of the sensor as an obstruction alarm to remind the reader to remove the obstruction blocking the transmitted light. The idea is structured.

Now, what is shown in FIG. 3 is the first embodiment of the present invention,
This is a transmitted light type smoke detector constructed based on the principle as described above.

That is, the projector side is constituted by a light emitting element 1 and a light emitting element pulse drive device 3 that drives the light emitting element 1 in pulses.

On the other hand, the light receiver side includes a light receiving element 2 disposed opposite to the light emitting element 1, an amplifier 4 for amplifying the minute output of the light receiving element 2 to a practical level, and this amplifier 4. and an A-D converter 5 that converts the output of the A-D converter 5 into a digital signal. The two different outputs of the discriminator 9 are connected to the fault alarm device 10 and the fire alarm device 11, respectively.

Next, to explain its operation, the light emitting element pulse driving device 3
When one pulsed light is emitted from the light emitting element 1, the transmitted light passing through the smoke measurement space is received by the light receiving element 2, and the light receiving element 2 outputs a minute signal according to the amount of light received.

After this signal is amplified to a practical level by an amplifier 4, it is converted from an analog quantity to a digital quantity by an A-D converter 5, and is temporarily stored in a storage device 6.

Next, when another pulsed light is emitted from the light emitting element pulse driving device 3, the light receiving element 2, the amplifier 4, and the A
A digital amount corresponding to the amount of transmitted light received at that time is obtained through the -D converter 5.

Here, at time t1 when the first pulsed light is emitted, the amount of received transmitted light obtained by the pulsed light is Dl, and
After the time when the second pulsed light is emitted, the amount of received light is D.
If it is 2, the calculation is performed by the slope calculator 7, and the slope K of the attenuation curve of the transmitted light is obtained.

This slope K is the smallest slope B that is already set in the first discriminator 8 and is considered to be a fire.
If it is not B or K, the smoke density is ignored as there is no change, and if it is B or K, the process is transferred to the subsequent second discriminator 9.

This discriminator 9 compares the slopes A and K, which are the largest inclinations that can be considered as a fire, and if A>K, it is determined that there is a fire, and the fire alarm device 11 is activated to issue an alarm.

Also, if A>K, the failure alarm device 10 is operated assuming that the transmitted light is blocked by an obstacle or the like,
Issue a fault alarm.

Next, FIG. 4 shows an example in which the arithmetic/control device 12 in the embodiment shown in FIG. 3 is configured by a CPU.

Note that FIG. 5 is an example of a flowchart showing the operation of the CPU.

The operation will be explained in Fig. 4 and Fig. 5 showing the flowchart.
This will be explained according to the diagram.

First, a command for emitting the first pulsed light is sent to the light emitting element pulse driving device 3 by a trigger pulse, and thereby the light emitting element 1 emits pulsed light.

The transmitted light that has passed through the smoke measurement space is transmitted through the light receiving element 2, the amplifier 4, and the A-
The D converter 5 converts it into a digital signal indicating the amount of received light, and the amount of received light is stored as data in the memory F according to a command from the CPU.

Thereafter, a certain period of time is counted (3 seconds in this example), then a command is issued to emit the second pulsed light, and the amount of light received at that time is stored in the memory G.

Then, in the next step, the slope K is calculated, and if B<K is not satisfied, the change in smoke density is assumed to be small, and after transferring the contents of memory G to memory F, the process merges with the "'wait3sec" step. ing.

The reason why the contents of memory G are moved to memory F is to obtain the slope each time the pulsed light is emitted.

Then, when there is no smoke at all or when the slope K is minute, the above operation is repeated.

Furthermore, when B<K is satisfied, it is possible that the fire may be caused by a fire or an obstacle, and the next judgment A>K is made as there is a possibility of a fire.

At this time, if A>K is satisfied, the slope K will satisfy A>K>B, so the fire alarm device is activated.

Further, if A>K is not satisfied, it is determined that the problem is caused by an obstacle, etc., and the obstacle alarm device is activated.

Next, FIGS. 6 to 10 are explanatory diagrams of a method for inspecting a transmitted light type smoke detector according to the present invention.

Operation tests are essential for not only smoke detectors but all detectors, etc., in order to improve their accuracy and prevent false alarms. The test equipment will be explained.

FIG. 6 shows a method for testing a conventional smoke detector that is configured to operate when the amount of light received exceeds a set value.

In this type of smoke detector, the smoke density value itself is a problem, so the film 13 corresponding to the desired smoke density is
All you have to do is put it in the optical axis and check whether the smoke detector works or not.

Incidentally, the change in transmittance before and after inserting the film is shown in FIG. 7, where a indicates the time when the film is inserted.

However, the above-described film-based inspection method cannot be applied to a transmitted light type smoke detector that operates based on the attenuation rate of transmitted light as in the present invention.

Therefore, a possible solution is to use a liquid crystal plate whose turbidity changes depending on the applied voltage, and by increasing the turbidity of this liquid crystal plate at an arbitrary slope over time as shown in Figure 8, it is possible to Changes in smoke density can be reproduced.

FIG. 9 shows an example of a circuit of an inspection device that generates a voltage to be applied to a liquid crystal plate, and is configured so that the output voltage increases linearly with time as shown in FIG. 10.

However, to explain its operation, when the switch SW is closed, there is no charge in the capacitor C□, and no voltage is applied to the base (point a) of the transistor Tr.
The transistor Tr is in a cut-off state, and no current flows through the resistor Th2 connected between the emitter and ground.
No voltage is generated at one end, point C.

On the other hand, the capacitor C2 is charged through the diode D, and the point b is charged to the vicinity of the power supply voltage Vcc.

Now, when the switch SW is opened at t=0, the capacitor C
1, a charging current flows through transistor Tr's base potential (a
point) begins to rise, a base current flows through the transistor Tr, a collector (emitter) current flows, and the emitter potential also gradually rises.

If the capacitance of the capacitor C2 is made sufficiently larger than that of the capacitor C□, the charge stored in the capacitor C2 will not change instantaneously, and the voltage at one end of the capacitor C2 will be the voltage at the emitter C of the transistor Tr. It rises in the same way as the point.

In addition, the increase in voltage at the three base points of the transistor Tr causes the same amount of voltage to increase at the emitter C point, and as a result, a constant voltage is applied across the resistor R□, and a constant current is applied to this resistor R□. 1c flows.

Now, since the amplifying circuit using the transistor Tr is an emitter follower, if the input impedance is set to be high enough, the constant current Ic flowing through the resistor R□ is all transferred to the capacitor C1.
It is thought that it will flow to

Therefore, the terminal voltage Vc of the capacitor C1 is expressed as , and changes linearly with respect to time t as shown in FIG. It can be changed.

In the actual operation test, the liquid crystal plate as described above is inserted into the optical axis of the transmitted light type smoke detector and the test is performed.As described above, in the transmitted light type smoke detector of the present invention,
It is configured to detect whether the smoke detector is activated due to a fire or an obstruction by using the speed of attenuation of transmitted light as the smoke concentration changes, so it is possible to detect whether the smoke detector is activated due to a fire or an obstruction. If the transmitted light is blocked, it can be known, and sources of false alarms such as obstacles can be eliminated.

Further, if an obstacle enters the measurement space, a fire alarm will not be issued, and false alarms can be prevented.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram of a conventional example, Fig. 2 is an explanatory diagram of the operating principle of the present invention, Fig. 3 is an embodiment of the present invention, and Fig. 4 is a configuration of the embodiment of Fig. 3 using a CPU. Figure 5 is a flowchart showing the operation of the CPU in Figure 4, Figures 6 and 7 are explanatory diagrams of the conventional inspection method, Figure 8 is a characteristic diagram of the liquid crystal panel, and Figure 9 is an operation test. An example of the circuit of the device, FIG.
It is a drawing which shows the output change of a figure. 1... Light emitting element, 2... Light receiving element, 3
...Developed optical element pulse drive device, 4...Amplifier, 5...A-D converter, 6...Storage device, 7... Slope calculator, 8.9...Discriminator, 10...Fault alarm device, 11...
... Fire alarm device, 12 ... Arithmetic/control device.

Claims (1)

[Scope of utility model registration request] A light-emitting element, a light-emitting element pulse drive device for pulse-driving the light-emitting element, a light-receiving element for receiving light from the light-emitting element, an amplifier for amplifying the output from the light-receiving element, and an amplifier for amplifying the output from the light-receiving element. A- converts the output from the device into a digital signal
D converter and the time when the light emitting element emitted the first pulsed light, Dl is the received amount of transmitted light obtained by the pulsed light, and the time when the second pulsed light is emitted. t2? If the amount of received light is D2, (D2 Di)
/(t2-ti) and determines whether this value is within a desired value range, and an alarm means that issues an alarm in response to a signal from the determination means. Transmitted light smoke detector.