JPS605435Y2 - ionization smoke detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to ionization smoke detectors, and particularly relates to preventing malfunctions caused by fog or condensation.

Conventionally, ionization-type smoke detectors have an intermediate electrode placed between positive and negative electrodes, and the same or different radioactive materials are ionized between the positive electrode and the intermediate electrode and between the intermediate electrode and the negative electrode, respectively, to cause an ionic current to flow. The distribution of ion current changes due to the intrusion of ions, and the ratio of the voltage drop between the positive electrode and the intermediate electrode and the voltage drop between the intermediate electrode and the negative electrode changes, and the smoke detection signal is generated by detecting the change in the potential of the intermediate electrode. It is configured to emit.

Therefore, if particles other than smoke, such as fog, enter between the positive electrode and the intermediate electrode, or between the intermediate electrode and the negative electrode, or both, the potential of the intermediate electrode changes in the same way as when smoke enters, causing the smoke to disappear. There is a risk of emitting a sensing signal.

Furthermore, if condensation occurs on the surface of the radiation detection material used for ionization due to sudden changes in temperature, radiation will no longer be emitted and the sensor will operate unstable, resulting in false alarms or missed alarms ( There is a risk that the alarm may not be issued even though smoke has been generated.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional drawbacks and provide an ionization type smoke detector that is free from malfunction.

The sensor of the present invention is an ionization type smoke sensor that includes an intermediate electrode between both positive and negative electrodes, and outputs a smoke detection signal by detecting a potential change of the intermediate electrode due to a change in ionic current caused by intrusion of smoke. The present invention is characterized in that a dew condensation sensor is provided and the smoke detection signal is not output based on the moisture detection signal of the dew condensation sensor.

Incidentally, it is possible to prevent false alarms by also using a heat-sensitive means that outputs an output when the temperature exceeds a certain level.

Next, the present invention will be explained in detail with reference to the drawings.

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

That is, the intermediate electrode 3 between the anode 1 and the cathode 2 of the ionization type smoke detector is connected to the gate of the field effect transistor 4, the drain of the transistor 4 is connected to the anode, and the source is connected to the anode through the resistor 5 and the Zener diode 6. Connect to the gate of thyristor 7.

On the other hand, a dew condensation sensor 8 and a resistor 9 are connected in series between both positive and negative alarm wires (not shown).

The anode and cathode of the thyristorph are also connected between the same two lines.

The connection point between the dew condensation sensor 8 and the resistor 9 is connected to the base of a transistor 10, the collector of the transistor 10 is connected to the connection point between the resistor 5 and the Zener diode 6, and the emitter is connected to the negative side of the alarm line. There is.

In the smoke detector configured as above, for example, smoke is detected at the electrode 2.
When the ions enter between the electrode 3 and the electrode 3, the potential of the electrode 3 rises due to the adsorption of ions between the electrodes 2 and 3, and the transistor 4 turns on, driving the thyristor 7 via the Zener diode 6. However, the thyristor 7 becomes conductive.

Detecting the occurrence of smoke is the same as in the conventional method.

However, when dew condensation occurs due to dew or a sudden change in temperature, the resistance value of the dew condensation sensor 8 becomes small, so the transistor 10 turns on and short-circuits the connection point between the resistor 5 and the Zener diode 6 to the negative side.

Therefore, since the Zener diode 6 is in an off state, the gate of the thyristor 7 is not triggered.

In other words, there is an effect that even if the potential of the smoke sensor increases due to fog or the like, no smoke detection signal is output.

It is desirable that the dew condensation sensor 8 is a sensor that does not change much in response to increases in humidity, but whose resistance rapidly decreases in response to the generation of moisture due to dew condensation or the like.

In the above-described embodiment, the smoke detector does not operate while the dew sensor is operating due to fog or the like, so even if a fire occurs during that time, there is a risk that an alarm will not be issued.

In order to solve this problem, the embodiment shown in FIG. 2 uses a heat-sensitive element such as a bimetal to issue a fire alarm when the temperature exceeds a certain level, regardless of the occurrence of smoke or fog.

In this case, the Zener diode 6 is connected to the base of the transistor 11, the emitter of the transistor 11 is connected to the ground line, and the collector is connected to the positive line via the resistor 12.

Then, the collector of transistor 11 is connected to transistor 1.
The collector of the transistor 13 is connected to the ground line through a resistor 14, and the emitter is connected to the positive line through a resistor 15.

The collector of the transistor 13 is also input to one side of an OR circuit 16, and the other input of the OR circuit 16 is connected to the positive line via a heat-sensitive contact 17 such as a bimetal.

The thyristor 7 is driven by the output of the OR circuit 16.

The heat-sensitive contact 17 made of bimetal or the like constitutes a heat-sensitive means that closes the contact when the temperature exceeds a certain level due to a fire.

In the above-described smoke detector, even when fog or the like is generated, the thyristor 7 is activated when the heat-sensitive contact 17 closes due to a rise in temperature due to a fire, so it is possible to generate the minimum necessary alarm.

It also has the advantage of being able to warn against fires that do not produce smoke.

Of course, when there is no fog generation, smoke can be detected by changing the potential of the electrode 3 as in the conventional case.

Moreover, if the heat-sensitive means is constituted by a heat-sensitive thyristor, it is possible to integrally attach it to a circuit board or the like, which has the advantage of facilitating manufacturing.

Further, there is no risk of contact failure or the like occurring.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing one embodiment of the present invention, and FIG. 2 is a circuit diagram showing another embodiment of the present invention. In the figure, 1... anode, 2... cathode, 3... middle electrode, 4... field effect transistor, 5°9, 12. 14. 15...
...Resistor, 6...Zener diode, 7...
... Thyristor, ... Condensation sensor, 10,
11.13...Transistor, 16...
・OR circuit, 17...Heat-sensitive means.

Claims (3)

[Scope of utility model registration request] (1) In an ionization type smoke sensor that includes an intermediate electrode between both positive and negative electrodes and outputs a smoke detection signal by detecting potential changes of the intermediate electrode due to changes in ionic current caused by intrusion of smoke, a dew condensation sensor is provided. An ionization type smoke sensor characterized in that the smoke detection signal is not output based on the moisture detection signal of the dew condensation sensor. (2) Utility Model Registration Scope of the Claim The ionization type smoke detector according to claim 1 is provided with a heat sensitive means that outputs an output when the temperature exceeds a certain level, and is configured to issue a fire detection signal when the heat sensitive means outputs an output. What I did. (3) Utility Model Registration The ionization type smoke detector according to claim 2, wherein the heat-sensitive means is constituted by a heat-sensitive thyristor.