JPH0542039B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a moisture-proof structure for an ionization type smoke detector that prevents moisture from entering a circuit housing portion.

[Prior art] Conventionally, this type of ionization smoke detector has
For example, the one shown in FIG. 11 is known.

In FIG. 11, 1 is a main body cover, 2 is an outer cover, and the outer cover 2 has a smoke inlet 3 formed therein.

Inside the sensor cover composed of the main body cover 1 and the outer cover 2, an inner electrode 6 with a radiation source 5, an intermediate electrode 8 with a through hole 7, and an external An external electrode 9 into which smoke can flow is incorporated, forming an electrode structure for ionization smoke detection.

A printed circuit board 10 on which a sensor circuit is mounted is housed on the back side of the insulating plate 4, and the housing portion of the printed circuit board 10 is sealed by inserting a rubber gasket 11 between the lower insulating plate 4 and sealing the upper cover 12 with the same rubber gasket 13. It is installed with a seal to prevent moisture and corrosive gases from entering from the outside.

[Problems to be Solved by the Invention] However, the moisture-proof structure of the circuit housing part in such conventional ionization type smoke detectors uses rubber packing, so the number of parts increases and The assembly work is complicated, and the size of the sensor in the height direction increases due to the inclusion of the gasket, which is a factor that prevents miniaturization of the sensor.

In addition, because relatively large circuit elements such as FETs and capacitors were mounted on the printed circuit board, the use of rubber gaskets meant that the circuit storage area became large, which also hindered the miniaturization of the sensor. was.

[Means for Solving the Problems] The present invention has been made in view of the problems of the conventional art, and it is possible to make the circuit housing part moisture-proof with a simple structure without using a gasket, and also to reduce the size of the sensor. The purpose of the present invention is to provide a moisture-proof structure for an ionization type smoke detector that can improve the temperature of the smoke sensor.

In order to achieve this object, the present invention provides an insulating plate in the cover to which an internal electrode with a radiation source, an intermediate electrode, and an external electrode with a smoke inlet are attached, and on the back side of the insulating plate. In an ionization type smoke detector having a structure in which a circuit board is housed, the insulating plate has a shape in which a ring-shaped fitting flange is integrally formed around the insulating plate, and the ring-shaped fitting flange of the insulating plate is formed before being assembled. The ring-shaped fitting flange is compressed by pressing into the fitting groove on the cover side, and is pressed into the groove.

[Function] The moisture-proof structure of the present invention with such a configuration can be assembled by simply pushing the ring-shaped fitting flange integrally formed around the insulating plate into the fitting groove on the cover side. , the circuit storage section can be sealed from the outside, and sealing means such as rubber gaskets are not required.

[Embodiment] FIG. 1 is a sectional view showing an embodiment of the present invention.

In FIG. 1, 1 is a main body cover, and 2 is an outer cover, each of which is made of synthetic resin, and a smoke inlet 3 is formed around the outer cover 2.

An insulating plate 14 having a structure shown in FIGS. 2, 3 and 4 is incorporated into the sensor cover consisting of the main body cover 1 and the outer cover 2. That is, the insulating plate 4 has a shape in which a ring-shaped fitting flange 15 is integrally formed on the outer periphery, and the ring-shaped fitting flange 15 of the insulating plate 14 is inserted into the fitting groove 16 of the main body cover 1 from below. It is assembled in a pressed state under the pressure of the outer cover 2.

An internal electrode 17 equipped with a radiation source is fitted and fixed in the center of the front side (lower side) of an insulating plate 14 incorporated in the sensor cover, and an intermediate electrode 17 with an opening hole is provided at a position covering the outside of the internal electrode 17. The electrode 18 is assembled, and an external electrode 19 is further attached to cover the outside of the intermediate electrode 18 and allow smoke to flow in from the outside.

Furthermore, an FET storage section 22 surrounded by a partition wall 21 is integrally formed on the back side of the insulating plate 14, and the FET storage section 22 is surrounded by a partition wall 21.
Inside the storage section 22 is an FET 2 used for the sensor circuit.
3 is incorporated, and the outside of the lead of the FET 22 is covered with synthetic resin hot melt or the like and fixed in place in a potting state.

Further, in this embodiment, a capacitor housing portion 24 is integrally formed at a predetermined position on the back side of the insulating plate 14.

A printed circuit board 25 is mounted in close contact with the back surface of the insulating board 14, which serves as a circuit storage section, and a capacitor 26 stored in the capacitor storage section 24 and an FET 23 installed in the FET storage section 22 in a potting state are attached to the printed circuit board 25. is connected.

Furthermore, an insulating board 1 incorporating a printed circuit board 25
A shield plate 27 is incorporated in the upper part of the circuit housing section on the back side of the circuit board 4.

2 shows the insulating plate 14 shown in the embodiment shown in FIG. 1, FIG. 3 shows a plan view of the back side of FIG. 2, and FIG. The top view of the figure is shown.

As is clear from FIG. 2, the insulating plate 14 is integrally formed with a ring-shaped fitting flange 15 extending toward the back side on its outer periphery. It has a molded shape that is bent outward and expanded in diameter. Further, an electrode mounting hole 28 into which the internal electrode 17 is press-fitted is formed in the center of the insulating plate 14, and a concave-convex ring portion 29 is formed on the outside of the electrode mounting hole 28 to ensure creepage distance between the electrodes. A through hole 30 is formed in the concavo-convex ring portion 29 at a position where the electrode lead provided on the intermediate electrode 18 is to be fitted, into which the electrode lead is inserted in close contact with the back side.

Further, on the back side of the insulating member 14, an FET housing part 22 for housing the FET in a potted state is formed surrounded by a partition wall 21, and on the opposite side of the FET housing part 22, a capacitor housing part 24 is formed. The shapes of the FET accommodating portion 22 and the capacitor accommodating portion 24 will become clearer from FIG.

In FIG. 3, the FET housing section 22 is located at the partition wall 21
It has a roughly elliptical shape surrounded by
A FET insertion hole 31 is formed, and a through hole 30 for an electrode lead of an intermediate electrode is opened inside.
Of course, an electrode mounting hole 28 for mounting an internal electrode is opened in the center of the insulating plate 14, and a capacitor storage portion 24 is formed on the left side of the electrode mounting hole 28. Furthermore, a pair of slits 3 for inserting and supporting the electrode leads of the external electrodes are provided at two symmetrical positions relative to the center.
2 is open.

On the other hand, the front side (lower side) of the insulating plate 14 shown in FIG. 2 becomes clear from the plan view of FIG. 4. That is, in order to secure creepage distance around the electrode mounting hole 28 in which the central internal electrode is mounted, the concave and convex ring portion 2 is
9 is formed concentrically, and has two fitting holes 33a and 33b, which are opened only on the surface side, at positions corresponding to the outer diameter of the intermediate electrode in the concavo-convex ring portion 29, and into which the supporting legs of the intermediate electrode are fitted. and a fitting hole 3 for fitting the electrode lead of the intermediate electrode to the back surface side.
A through hole 30 is opened in 3c.

The opening hole 34 on the left side of the protrusion corresponding to the capacitor housing 24 serves as a hole for mounting an LED as an alarm indicator from the inside, if necessary.

Next, referring to FIGS. 5, 6 and 7, the insulating plate 14
The moisture-proof structure of the circuit housing section will be explained in detail.

Figure 5 is a sectional view of the main body cover 1 shown in Figure 1.
This figure shows how the insulating plate 14 is assembled into the sensor cover consisting of the outer cover 2 and the outer cover 2, and a part of the electrode structure is omitted.

That is, the insulating plate 14 is assembled by fitting the ring-shaped fitting flange 15 formed on its outer periphery into the fitting groove 16 formed on the main body cover 1 side.
At the same time as 4 is assembled, a shield case 27 is installed in the circuit housing, and an external electrode 19 is installed in between.
The outer cover 2 is attached from below through.

As shown in FIG. 6 before assembly of the insulating plate 14, the tip of the ring-shaped fitting flange 15 is bent outward and expanded in diameter.
When this ring-shaped fitting flange 15 is pushed into the fitting groove 16 on the main body cover 1 side as shown by the arrow, the ring-shaped fitting flange 15 is pushed into the fitting groove 16 as shown in FIG.
The ring-shaped fitting flange 1 is assembled in a state in which it is compressed inward by pushing it against the
The tip is pressed against the outer slope of the fitting groove 16 by the reaction force caused by the tightening in step 5, and it is possible to reliably prevent moisture and corrosive gas from entering the circuit housing section located on the back side without using rubber gaskets or the like. can.

FIG. 8 is an enlarged half-sectional view of the FET storage section 22 in the embodiment shown in FIG.

As is clear from FIG. 8, the FET 23, which was conventionally mounted on the printed circuit board 25 after being potted, is placed inside the FET storage section 22 partitioned by the formation of a partition wall 21 on the back side of the insulating plate 14. One of the lead terminals of the assembled FET 23 is soldered to the electrode lead of the intermediate electrode 18, and the other lead is soldered to the printed circuit board 25 provided in close contact with the back side of the insulating plate 18. After soldering, the inside of the FET housing section 22 is filled with a potting material such as synthetic resin hot melt to seal it insulatingly and to reliably prevent electrostatic damage when touched during assembly.

In addition, conventional FET potting processing was performed on the FET alone as a pre-assembly process, but by forming the FET housing portion 22 on the insulating plate 14, potting can be performed through assembly on the insulating plate 14. In this respect as well, assembly man-hours can be reduced.

FIG. 9 shows the intermediate electrode 18 shown in the embodiment of FIG.
Figure 1A shows a plan view, and Figure 2B shows a side view.

That is, the intermediate electrode 18 has a ring-shaped electrode shape, has an electrode piece 18a extending inward to approximately the center, and further has support legs 3 at three locations on the outer periphery of the ring.
6a, 36b, and 36c are integrally formed in a bent state. Among these support legs 36a to 36c, for example, the support leg 36c has an electrode lead 37 extending therethrough as is clear from FIG. 9b.
This electrode lead 37 is pushed out to the back side in order to fit through the through hole 30 of insulating plate No. 1 shown in FIG. 4 and connect to the FET 23, for example. Further, as is clear from FIG. 9b, sawtooth-like unevenness is formed on the side surfaces of the support legs 36a to 36c, and the insulating plate 1
4 to prevent it from coming out when inserted.

FIG. 10 shows how the intermediate electrode 18 shown in FIG. 9 is assembled to the insulating plate 14, and there are openings in three places on the front side of the insulating plate 14 only on the front side as shown in FIG. Fitting holes 33a, 33b are formed in two places, and a fitting hole 33c with a through hole 30 is formed, and as shown in FIG. Insulating plate 1
4 can support the intermediate electrode 18. still,
FIG. 10 is a cross-sectional view taken along line XX in FIG. 4.

[Effects of the Invention] As explained above, according to the present invention, the insulating plate can be assembled by simply pushing the ring-shaped fitting flange integrally formed around the insulating plate into the fitting groove on the cover side. The circuit storage area formed on the back side can be sealed from the outside, and there is no need for a separate sealing means such as a rubber gasket, which reduces the number of parts and assembly man-hours.Also, the amount of circuit storage that does not use the gasket can be reduced. The dimensions of the section can be reduced.

Also, it is mounted on the circuit board on the back side of the insulating board.
Since the FET storage part that stores the FET in a potted state is formed integrally, there is no need to secure space on the circuit board side to store the FET in a potted state. The circuit board can be mounted closely,
This allows the height of the circuit housing portion to be reduced.

Furthermore, since the insulating plate has a through hole for fitting the electrode lead of the intermediate electrode on the back side and a fitting hole for supporting the intermediate electrode, it is extremely easy to assemble the intermediate electrode to the insulating plate, and the electrode lead can be inserted easily. Even if it is inserted into the back side, the electrode lead is sealed by potting, so the airtightness of the circuit housing part is not compromised.

By adopting these moisture-proof structures, the height dimension of the internal structure of the ionization type smoke detector can be shortened, and the overall size of the sensor can be significantly reduced.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of the present invention; FIG. 2 is a cross-sectional view of the insulating plate shown in FIG. 1;
Figure 3 is a plan view of the back side (upper side) of Figure 2; Figure 4
The figure is a plan view of the front side (bottom side) of Fig. 2; Fig. 5 is a sectional view showing the state in which the insulating plate is installed in Fig. 1; Fig. 6 is the state before the insulating plate is installed in Fig. 5. Figure 7 is an explanatory diagram when the insulating plate is installed; Figure 8 is an enlarged half-sectional view of the FET storage structure in Figure 1 taken out; Figure 9 is an enlarged half-sectional view showing the intermediate electrode in Figure 1 taken out. FIG. 10 is a sectional view showing a structure in which an intermediate electrode is assembled to an insulating plate; FIG. 11 is an explanatory view of a conventional structure. 1: Main body cover, 2: Outer cover, 3: Smoke inlet, 14: Insulating plate, 15: Ring-shaped fitting flange, 1
6: Fitting groove, 17: Internal electrode, 18: Intermediate electrode,
19: External electrode, 21: Partition, 22: FET housing, 23: FET, 24: Capacitor housing, 2
5: Printed circuit board, 26: Capacitor, 27: Shield case, 28: Electrode mounting hole, 29: Uneven ring part, 30: Through hole, 32: Slit, 33a
~33c: Fitting hole, 34: Through hole (for alarm indicator light), 36a~36c: Support leg, 37: Electrode lead.

Claims (1)

[Scope of Claims] 1. A structure in which an insulating plate is provided inside the cover, on which an internal electrode with a radiation source, an intermediate electrode, and an external electrode with a smoke inlet are attached, and a circuit board is housed on the back side of the insulating plate. In the ionization type smoke detector, the insulating plate has a shape in which a ring-shaped fitting flange is integrally formed around the insulating plate, and the ring-shaped fitting flange of the insulating plate has its tip facing outward before being assembled. Moisture-proofing of an ionization type smoke detector, characterized in that the ring-shaped fitting flange is pressed into a fitting groove on the cover side and pressed into the groove. structure.