JPS58171660A - Ionization type smoke sensor - Google Patents

Abstract

PURPOSE:To obtain a smoke sensor having an ion room not bringing about a leakage current, by attaching a cathode electrode to a printed-circuit board in the ion room via a guard electrode. CONSTITUTION:A terminal 3a of a cathode electrode 3 is inserted into a through-hole 5a of an insulator 5. A collar part of the insulator 5 is engaged by an engaging claw 4c of a guard electrode 4. The electrode 4 is engaged with an entrance of a fitting hole 6a of a printed-circuit board 6 by an engaging claw 4b. Besides, the electrode 4 is connected to an electrically conductive pattern of the plate 6 and is earthed through the plate 6. A projecting piece 2b of an anode electrode 2 is inserted into a through-hole 6b of the plate 6 and also, is connected electrically conductively to a signal processing circuit. A path of a leakage current from the anode 2 to the cathode 3 in an ion room is as follows; anode electrode 2 printed-circuit board 6 guard electrode 4 insulator 5 cathode electrode 3. Further, said current is transmitted from the plate 6 to the electrode 4 and all of it is earthed. As a result, the leakage current is not moved from the insulator 5 to the cathode 3.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an improvement in the ion chamber of an ionization smoke detector.

For example, the ionization type smoke sensor W# has one ion chamber.
If it is an f-yamper type, as shown in Figure 1, the ion chamber IK power supply voltage is applied, and the ion chamber IK smoke enters, causing an increase in current! Fog decreases.

As a result, the output voltage Voot also decreases, and the signal processing circuit A detects this voltage change and sends a reception lIl[signal.

Figure 8 (1) When the O equivalent I circuit KsP and the sensor are in the monitoring state, the impedance RI of the turtle's ion chamber 1 is set to a high value, but the ion chamber 1 is formed. If moisture or dirt adheres to the anode electrode 2
Leakage current I other than the current Is between the electrode 8 and the cathode electrode 8
Since m flows through the surface and inside of the insulating member, for example, an ionic current Is of about 100 PA flows, and the ionic current Is decreases by ~■% due to smoke. Output 1i pressure Too
t 411-110 If the setting is such that the color alarm force is activated when m decreases, if the leakage current 1 m is about 100 PA, the ion current Is will be the same as 200 Pm, and the ion current Is will be I~ The sensor will not operate even if it decreases by about 1%.

This causes leakage current! Conventionally, in order to prevent
), a guard voltage [4] is integrated with an insulator 5, and its pin 7 is disposed inside the ion chamber, and the leakage current Im from the anode to the cathode 8 flows into the guard voltage 1i4 and is grounded. However, the lower surface of the insulator 6 has one node electrode 2, a cathode electrode ff18. Each electrode of the guard electrode 4 is exposed on the surface, and current leaks along the paths of arrows A, B, C, etc., and in the equivalent circuit Ii1 of FIG. 2(b):
It is conceivable that the leakage current Im will increase and affect the operating characteristics.

In view of the above-mentioned problem K11, the present invention #i is a book aimed at providing a sensor having an ion chamber that does not generate a flooding current Im'.

The following is a summary of this idea! To explain with reference to FIGS. 4 and 6 shown as examples, in FIG. 4, the printed board 6 has a fitting hole 6a formed in the center, and a plurality of through holes 6b, 6b, . ... has been established.

It forms the outer shell of the ion chamber l, and has a cylindrical shape with an opening at the bottom of the anode tFMsIVi which also serves as an electrode, and has multiple smoke inflow holes of 2 m at the upper side of the side, c... and multiple protruding pieces at the lower side of the side. 2b, 2b,... are formed.

The cathode WfMS has a plate shape with a through hole in the center, through which an L-shaped terminal 8 is inserted and conductively coupled, and a radioactive substance 8b is fixed on the upper surface. The insulator 5 has a brim and a through hole 5a in the center through which the terminal 8& is inserted. The guard pole 4 is a conductor and has a hole in the center of the plate.
A plurality of engaging claws 4b, .
C1... is provided.

As shown in FIG. 6, the above-mentioned structural members allow the electrode terminal 8 to be inserted into the through hole 5m of the insulator 6. The collar portion of the insulator S is engaged by the engagement claw 4CK of the guard electric terminal 1i4. Then, the guard electrode 4 is engaged with the opening IIkFc of the fitting hole 6 of the printed board 6 through the engaging claw 4hK, and connected to the conductive pattern (not shown) of the printed board, and the anode electrode is grounded via the printed board. XFi Central Outlet! b is inserted into the through hole 6 of the printed board 6 and conductively connected to the signal field circuit.

In the above ion chamber IK configured as above, the meridian for leakage current from the anode to the cathode is the anode electrode snow-gudant plate @-ff-de electrode 4-insulator 6-cathode cell line. There is always a guard electrode 4 on this path, and after transmitting the signal from this printed board 6 to the guard electrode reef,
Since the electric current fM4 is all grounded, there is no flow from the insulator black to the cathode electrode 4.

In view of the above, in an ionization type smoke detector consisting of an anode electrode attached to a printed board to form an ion chamber, and a cathode electrode attached to the radioactive material inside the chamber,
An insulation type smoke sensor characterized in that a fitting hole for a cathode electrode supporting insulator is formed in the printed board in the ion chamber, and the insulator and the printed board are connected via a guard electrode. However, in the conventional ion chamber structure, leakage current may occur on the surface or inside of the insulator.

In the present invention, a guard electrode is always placed on a path where a leakage current is expected to occur, so that no leakage current occurs under normal usage conditions, and the reliability of the sensor is significantly improved. Also, the material of the insulator is also different! Compared to IIK, it does not require relatively high insulation performance, and is advantageous in that it can be selected from a wide range of materials.

[Brief explanation of the drawing]

Figure 1 is a circuit diagram of an ionization smoke detector, Figure 2 (ta)
ij 111i circuit diagram of the ion chamber without a guard electrode, Figure 2 (b) is an equivalent circuit diagram with a guard electrode attached, Figure 8 (turtle) #i Cross-sectional perspective showing the ion chamber of the conventional example 8(b) are a bottom view of the conventional example, FIG. 4 is an exploded perspective view of the ion chamber of the present invention, and FIG. 6 is a cross-sectional perspective view of the ion chamber of the present invention. Iton chamber for l, 2...anode electrode 1[, s...cathode electrode, sb...radioactive material%4-...! -do w1
．． Coffin, 6...Insulator, 6...Printed board, shaft...
Fitting hole. Patent Applicant Matsushita Electric Works Co., Ltd. Representative Patent Attorney Utamaru Takemoto (#1 Riki&! name) Figure 1 Figure 2 (Q) (b)

Claims (1)

[Claims] 1) In the ionization type smoke sensor #, which consists of an anode electrode attached to a printed board to form an ion chamber and a cathode electrode attached to the radioactive material inside the ion chamber, a. 1. An insulating type smoke detector, characterized in that a fitting hole is formed in an insulator, and the insulator and a glint plate are connected via a guard electrode.