JPS5831272Y2 - Ionic smoke detector - Google Patents

Description

[Detailed Description of the Invention] This invention relates to an ion type sensor in which a detection circuit is constituted by an IC.

In recent years, the detection circuits of ion-type smoke detectors have also been integrated into ICs, but for example, dual-in-line type (hereinafter simply referred to as DIP-type) ICs that use a dual-in-line package, in which many terminals are arranged close to each other in a straight line, Since the distance between each terminal is about 1 inch, the insulation between the input terminal connected to the high impedance connection point of the inner and outer ion chambers and other terminals deteriorates due to dirt and moisture, causing leakage current and malfunction. Or there was a risk of misreporting.

In view of the above points, this invention provides a reliable ion type smoke detector which does not malfunction or fail to report due to dirt or moisture between the C terminals and has a large detection output.

It is something. Figure 1 is a circuit diagram of an embodiment of this invented ion type smoke detector - 'c and co are outer ion chambers that allow smoke to advance, and CI is an inner ion chamber as a comparative element in a nearly sealed state. These are connected in series and connected in parallel with the resistor R to constitute a smoke detection section.

i is connected between the terminals of the fire detector and constitutes a smoke detection circuit that detects impedance changes in the external ion chamber CO;
It is an IP type IC, and is composed of a differential amplifier A, a comparator C, and an amplifier provided as necessary, or a delay circuit (not shown).

The inverting input of the amplifier A is connected to the connection point of both ion chambers C, O, and CI through the input terminal 4 of the IC, and the non-inverting input is connected to the I
A resistor R1 connected between the sensor terminals through terminal 1 of C
It is connected to the midpoint of the first voltage divider serving as a reference potential JR2, and is also connected to the terminal 3.5 of the IC adjacent to the input terminal 4 through a resistor R3.

Furthermore, the output of the differential amplifier A is connected to one end of the smoke detection section through the terminal 2 of the IC, and is also connected to one input of the comparator C.

The other input of the comparator C is connected via the terminal 6 of the IC to the midpoint of a second voltage divider for setting sensitivity made up of resistors R41R5, and the output is connected to the input of the amplifier.

Further, the output of the amplifier is connected to the gate of a thyristor S as a switching circuit connected between terminals of the fire detector, and the operation of the thyristor S causes a confirmation light to be turned on.

Next, the operation of the circuit shown in FIG. 1 will be explained with reference to the characteristic diagram of the smoke detection section shown in FIG. 2.

In FIG. 2, the horizontal axis E represents both ends of the smoke detection section and both ion chambers CO.

The potential at the connection point of CI is shown on the vertical axis ■, and the potential at the connection point of CI is each ion chamber CO, C.
The ionic current flowing through I is shown.

When power is applied between the sensor terminals and a voltage is generated across the resistor R through the ICI differential amplifier A, both ion chambers CO and C
Since this connection point is connected to the inverting input of the differential amplifier A and its output is connected to the smoke detection section, the potential at the connection point of I is determined by the negative feedback effect at the connection point of the resistors R, , R2. It is held at a constant potential equal to the potential.

To explain this state using FIG. 2, if the load curve of the internal ion chamber CI is 11 and the load curve of the external ion chamber CO is 12, then the potential at both ends of the smoke detection section and both ion chambers Co, C
The potential at the connection point of I is indicated by O, el, and e.

Since the potential e at the connection point of both ion chambers is equal to the potential at the connection point of resistors R1 and R2, there is no potential difference between terminals 4 and 3 or 5 of the IC connected to them.
Even if terminals 6 to 6 are contaminated, no leakage current flows between terminals 4 and 3 or 5, and terminals 3 and 5 act as protective electrodes for terminal 4, thereby preventing malfunctions in normal conditions.

In this state, when a certain concentration of smoke enters the external ion chamber CO and the impedance of this ion chamber CO increases, the load curve 12 changes to 12'.

Further, since no smoke enters the internal ion chamber CI, the load curve 11 is not changed.

Therefore, the potential at the connection point of both ion chambers CO and CI is changed from e to e.
However, the voltage across the resistor R instantaneously increases due to the negative feedback action of the differential amplifier A, so that the potential at the connection point between both ion chambers CO and CI becomes equal to that of the IC to which it is connected. A state in which the potential e equal to the potential of the terminal 3.5 adjacent to the terminal 4 is held constant, that is, the potential e at one end of the smoke detection part without any leakage current flowing, is determined by the load curve 12// e1 ’.

A predetermined change in the potential of the smoke detection section is detected by a comparator C, and its output is amplified by an amplifier to operate a thyristor S, so that a confirmation light is turned on or a fire signal is sent to a receiver (not shown).

In this example, the voltage across the internal ion chamber CI was held at a constant voltage to keep the potential at the connection point between both ion chambers CO and CI constant; however, the voltage across the external ion chamber CO was kept constant and both It is also possible to keep the potential at the connection point between the ion chambers Co and CI constant.

In this case, the potential change at one end of the smoke detection section is smaller than in the above embodiment.

Further, in the above embodiments, the smoke detection section is configured with a series circuit of the internal ion chamber CI and the external ion chamber CO, but it can also be configured with a series circuit of a high resistance value resistor and the external ion chamber CO.

As described above, this invention is designed to meet the needs of both ion chambers at the connection point, i.e., the I
Since the input terminal of C is held at a constant potential, there is no potential difference between this input terminal and the adjacent terminal of the IC used as a protective electrode, and no leakage current flows between these terminals. Even if an IC is used, a reliable ion smoke detector can be obtained that will not malfunction or fail due to dirt between its terminals.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of the ion type smoke detector of this invention, and FIG. 2 is a characteristic diagram of FIG. 1. CO: external ion chamber, CI: internal ion chamber as a comparison element, i: IC1A: differential amplifier,
C... Comparator, 1-6... IC terminal, R,
. R2J R45R5...Resistance, S...Sirisk.

Claims (1)

[Scope of utility model registration request] Smoke detection part ≦ Comparison element, example? C, (4) The external part that allows smoke to enter, the ion chamber, and the circuit that detects impedance changes in this chamber has a large number of terminals placed close to the straight line. In the sensor, the above-mentioned IC is composed of at least a differential amplifier and a comparator, 1. One input of the above-mentioned differential amplifier is connected to a connection point between a comparison element and an external ion chamber through an input terminal of the IC;
The other input is connected between the terminal of the fire detector through the terminal of the IC (this is connected between the midpoint of the voltage divider as a reference potential and the terminal of the IC adjacent to the input terminal), and the output is connected to one side of the comparator. The input and q are connected to the lower end of the smoke detector above through the IC terminal, and the other input is connected to the voltage divider for sensitivity setting, which is connected to the fire detector terminal through the IC terminal. 1. An ion type smoke detector, characterized in that the output thereof is connected to the input of a switching circuit.