JPS6023302B2 - ionization smoke detector - Google Patents

Description

[Detailed description of the invention] This invention relates to an ionization type smoke detector.

A conventional ionization smoke detector is shown in FIG.

In Figure 1, 1 is an oscillation circuit, 2 is an ion chamber, 3 to 5 are resistors, 6 is an amplifier circuit, 7 is a transistor, 8 is an integrating resistor, 9 is an integrating capacitor, and 10 is a PU
T (trigger element), 11 to 14 are resistors, 1
5 is a thyristor (switch element), 16 and 17 are sensor terminals, and 18 is a constant voltage circuit to which a DC voltage is applied from a sensor line. Next, the operation of this ionization type smoke sensor will be explained with reference to FIG.

The DC voltage applied from the sensor terminals 16 and 17 is converted into a constant DC mother pressure by the constant voltage circuit 18. When this constant DC voltage is applied to the oscillation circuit 1, the transistor la
, lb are operated, and from each anode side, FIG. 2A,
A pulse voltage as shown in FIG. 2A is generated, and the pulse voltage in FIG.
The pulse voltage shown in FIG. 2B is amplified and waveform-shaped by the transistor ld and converted into a pulse voltage as shown in FIG. 2C. The pulse voltage passing through the transistor c charges the integrating capacitor 9 via the integrating resistor 8, and the pulse voltage passing through the transistor d passes through the ion chamber 2 and is amplified by the amplifier circuit 6, and the voltage is amplified by the amplifier circuit 6 as shown in FIG. At the same time, the DC component is removed and the result is as shown in Fig. 2E. This pulse voltage shown in FIG. 2E becomes the base voltage of the transistor 7. At all times, that is, when no smoke enters the ion chamber 2, a large amount of current flows through the ion chamber 2, and therefore the base voltage of the transistor 7 is higher than the threshold level (0.6V), turning the transistor 7 on, and the integral The voltage across the capacitor 9 does not rise above the voltage divided by the high resistors 11 and 12, and the PUTI O maintains the cut-off state, and as a result, the thyristor 15 also maintains the cut-off state.

Now, in an emergency, that is, when a bonito enters the ion chamber 2, the current flowing through the ion chamber 2 decreases, and the base voltage of the transistor 7 becomes lower than the threshold level (0.6V), and the transistor 7 It becomes off state, and the voltage across the integrating capacitor 9 becomes high resistance 1.
The voltage becomes higher than the voltage set in 1 and 12, and PUTI O
is in the conductive state, and as a result, the thyristor 15 is in the conductive state. This ionization smoke detector generates smoke and the PU
After the TIO and thyristor 15 have worked, in order to restore the circuit, the voltage application to the sensor terminals 16 and 17 is temporarily stopped to cut off the thyristor 15, and then the voltage is applied to the sensor terminals 16 and 17 again. However, PUTI0 continues to be on due to the discharging current of the integrating capacitor 9, and a current that does not trigger the thyristor 15 is flowing.

The reason for this is that, as shown in the equivalent circuit in Figure 3, when the string source is turned on (V, = 10V), the current lc that flows through the high resistor 11 is only a minute current, so the transistor TR
2 is turned on and PUTIO continues to be in the conductive state. As a result, there was a problem that the device would not operate normally even if smoke entered the device next time. However, if the voltage application to the sensor terminals 16 and 17 is stopped for a sufficiently long time, the discharge current of the integrating capacitor 9 will become less than the holding current of PUTIO, and PUTI
However, considering the commonly used recovery switch, the PUT 10 cannot be used as shown in FIG. In order to completely cut off PUTIO when the power is turned on, it is sufficient to increase the current lc on the collector side of the transistor TR2 so that the minute current IB flowing through the transistor TR does not allow the current lc to flow completely through the transistor TR2.

By doing so, the transistor TR2 is cut off, and at the same time, the gate potential of PUTIO rises, and the PUTI stream is completely cut off. Circuits shown in FIGS. 4A, B, and C have been proposed as circuits for increasing this current lc. Fourth
Figure A uses low resistances 19 and 20 instead of high resistances 11 and 12, and Figure 4B uses low resistance 21 and Jenner diode 22 instead of high resistances 11 and 12, respectively. However, each has the disadvantage of increased current consumption. On the other hand, in FIG. 4C, a low resistance 23 and a high resistance 24 are used in place of the high resistances 11 and 12, respectively.
The current consumption was small, but the gate potential of PUTIO became high, making it impossible to set the threshold level of PUTIO. SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an ionization type smoke sensor that can be reset reliably, consumes less current, and allows easy setting of the threshold level of a trigger element.

An embodiment of the invention is shown in FIG. That is, this ionization type smoke sensor uses a Zener diode 25 and a high resistance 26 instead of the high resistances 11 and 12, respectively. To explain the operation of this embodiment, when the voltage V changes from a low level (approximately 0.6 V) to a high level (approximately 10 V) upon power-on, the fin flow initially
．． 6)/(R, 30R, 4), but in relation to the current IB, the transistor TR
2 is blocked.

Then, 1,=(
V. -V2)/R26, only a small current of about several tens of amperes flows, reducing current consumption. At the same time PUTI
The gate potential of O rises and PUTIO becomes increasingly cut off. However, R, 3, R, 4, and R26 represent the resistance values of the resistors 13, 14, and 26, respectively. As a result of this configuration, it is possible to flow a large amount of current to the gate of PUTIO at the time of re-operation, and it is possible to reliably turn off PUTIO and reset it at the time of re-operation.
Further, since the current flowing from the Zener diode 25 to the high resistance 26 is small, current consumption can be reduced. Furthermore, due to the Jenner voltage of the Jenner diode 25, P
Since the gate voltage of UTIO is determined, it is easy to set the threshold voltage of PUTIO. As described above, in the ionization type smoke detector of the present invention, the cathode of a Zener diode is connected to the positive sensor terminal, and a high resistance is connected between the anode of the Zener diode and the negative sensor terminal. The anode of the trigger element is connected to the integrating circuit, and the gate is connected to the Zener diode and the high resistance connection point, and when the output voltage of the integration circuit exceeds the voltage of the Zener diode and the high resistance connection point, Since the trigger output is generated from the cathode of the trigger element, resetting can be performed reliably, current consumption can be kept low, and the threshold level of the trigger element can be easily set. There is.

[Brief explanation of drawings]

Figure 1 is a circuit diagram of a conventional ionization smoke detector, Figure 2 is a waveform diagram to explain its operation, Figure 3 is an equivalent circuit diagram of the main part of Figure 1, and Figure 4 is a proposed example. A schematic diagram, FIG. 5 is a main part circuit diagram of an ionization type smoke detector according to an embodiment of the present invention,
The figure is its equivalent circuit diagram. 2...Ion chamber, 7...Transistor, 8...Resistor for integration, 9...Capacitor for integration, 10...・・・
・PUT (trigger element), 15... Thyristor (switch element), 16, 17... Sensor terminal, 25...
・Schener diode, 26...high resistance. Figure 2 Figure 3 Figure 4 Figure 5 Figure 6 Vertical

Claims (1)

[Claims] 1 positive and negative sensor terminals, a Zener diode with a cathode connected to the positive sensor terminal, a high resistance connected between the anode of the Zener diode and the negative sensor terminal, and an integrating circuit; When the anode is connected to the output end of the integrating circuit and the gate is connected to the connection point between the Zener diode and the high resistance, so that the output voltage of the integration circuit exceeds the voltage at the connection point between the Zener diode and the high resistance. A trigger element that generates a trigger output from the cathode, a switch element that conducts with the trigger output of this trigger element and short-circuits the positive and negative sensor terminals, and an ion chamber that detects smoke and reduces the amount of current. and a voltage that normally limits the output voltage of the integration circuit to a voltage below the voltage at the connection point between the Zener diode and the high resistance, and releases the restriction on the output voltage of the integration circuit in response to a decrease in the amount of current in the ion chamber. An ionization smoke detector with a limiting circuit.