JP5721550B2 - Photoelectric smoke detector - Google Patents

Description

  The present invention relates to a photoelectric smoke detector, and more particularly to a photoelectric smoke detector having a good S / N (signal / noise) ratio.

Conventionally, photoelectric smoke detectors are usually installed on ceilings such as indoors, and smoke detection means for detecting smoke that has flowed into the detector, and the occurrence of fire based on the detection results. Judging means for judging and notifying means for notifying the judgment result are provided. The smoke detecting means is composed of a light emitting element and a light receiving element, and detects the presence or absence or degree of light scattering by smoke particles flowing into the darkroom. The dark room is formed by a lid, a plate, and a labyrinth body that can be ventilated and shielded.
And in order to realize miniaturization of the photoelectric smoke detector, the dark room is formed in a cylindrical shape with one side projecting outward, a light emitting element is disposed in the projecting part, and the bottom surface and the outside of the dark room. A photoelectric smoke detector is disclosed in which a circuit board is disposed substantially in parallel and a light receiving element is installed on the circuit board in accordance with the position of a substrate hole formed in the center of the bottom surface (see, for example, Patent Document 1).

Japanese Patent Laying-Open No. 2006-244515 (page 7-9, FIG. 2)

However, in the invention disclosed in Patent Document 1, the light emitting element has an optical axis in a direction parallel to the circuit board, and the light receiving element has an optical axis in a direction perpendicular to the circuit board. Is 90 °. Therefore, when the detection wavelength is in the vicinity of 800 to 1000 nm, there is a problem that the amount of light scattered is small and the S / N ratio is poor.
Moreover, since the flow of smoke is hindered at the protruding portion, there is a problem that the uniformity of smoke inflow from all directions is hindered and the inflow property (directivity) is deteriorated.
Furthermore, the photodiode (hereinafter referred to as “PD”) that forms the light receiving element is housed (enclosed) in a shield case for shielding electrical noise, so that the number of components is increased and the manufacturing is performed. There was a problem of hindering cost reduction

  The present invention solves such a problem. Firstly, it aims to improve the S / N ratio and the inflow of smoke, and secondly, photoelectric smoke detection which realizes a reduction in manufacturing cost. The purpose is to provide a vessel.

(1) A photoelectric smoke detector according to the present invention includes a bottom plate having a penetrating optical base hole and a plurality of side plates that are erected on one surface of the bottom plate and arranged in an annular shape. An optical bench, an optical bench cover installed at an end of the side plate, a printed board on which the other surface of the bottom plate faces with a predetermined gap and a through-hole is formed, the bottom plate, Formed by a plurality of side plates and the optical base cover, installed in the dark room where the outside light cannot enter and smoke can flow in, and irradiates light of an optical axis substantially parallel to one surface of the bottom plate A light emitting element and a ground pattern that is provided on a surface of the printed circuit board that does not face the other surface of the bottom plate, shields electrical noise, and is mounted at the position of the substrate hole on the ground pattern; Irradiated by smoke particles in the darkroom A light receiving element for receiving Jill scattered light, and
The optical axis of the light receiving element is formed by penetrating the substrate hole and the optical platform hole, and the optical axis of the light emitting element and the optical axis of the light receiving element intersect at an obtuse angle in the dark room. To do.

In the photoelectric smoke detector according to the present invention, since the optical axis of the light emitting element and the optical axis of the light receiving element intersect with an obtuse angle, when the detection wavelength is in the vicinity of 800 to 1000 nm, the amount of scattered light is detected more. And the S / N ratio is improved.
Also, when the light receiving element is mounted on the ground pattern that is provided on the surface that does not face the bottom plate of the printed circuit board and shields electrical noise, the light receiving element is housed in a shielding case that shields electrical noise that has a light receiving hole. This reduces the number of parts and the manufacturing cost.
Furthermore, since the dark room is formed by the side plate and the optical bench cover that form a discontinuous annular labyrinth with the bottom plate, there is no barrier to block the inflow of smoke from a specific direction, so the dark room from all directions. Smoke does not flow in, and the inflow (directivity) does not deteriorate.

The top view explaining the photoelectric smoke detector which concerns on Embodiment 1 of this invention. The side view explaining the photoelectric smoke detector which concerns on Embodiment 1 of this invention. The perspective view which isolate | separates and shows the member explaining the photoelectric smoke detector shown in FIG. The perspective view which isolate | separates and shows the member explaining the photoelectric smoke detector shown in FIG. Sectional drawing of the side view explaining the photoelectric smoke detector shown in FIG. Sectional drawing of planar view explaining the photoelectric type smoke sensor shown in FIG. The top view explaining the photoelectric smoke detector which concerns on Embodiment 2 of this invention. The perspective view which isolate | separates and shows the member explaining the photoelectric smoke detector shown in FIG. Sectional drawing of the side view explaining the photoelectric smoke detector shown in FIG.

[Embodiment 1]
Hereinafter, the photoelectric smoke detector according to Embodiment 1 of the present invention will be described with reference to the drawings. In addition, in each figure, the same code | symbol is attached | subjected to the same part and some description is abbreviate | omitted.
1 to 6 illustrate a photoelectric smoke detector according to Embodiment 1 of the present invention. FIG. 1 is a plan view, FIG. 2 is a side view, and FIG. 4 is a perspective view showing the members separately, FIG. 5 is a sectional view in side view, and FIG. 6 is a sectional view in plan view.

1 to 6, the photoelectric smoke detector 100 includes a bottom plate 12 in which a penetrating optical platform hole 11 is formed, and a plurality of side plates 13 erected on one surface 12 a of the bottom plate 12. A printed circuit board 20 that faces the optical table 10, the other surface 12 b of the bottom plate 12 at a predetermined interval, and has a through-hole 21 formed therein, and an optical table cover 30 that is installed at the end of the side plate 13. ,have.
A dark room 60 is formed by the bottom plate 12, the plurality of side plates 13, and the optical bench cover 30. The plurality of side plates 13 each have a T-shaped cross section or a Y-shaped cross section, and form a labyrinth (maze) that does not allow outside light to enter the dark room 60 although air can pass through the gaps between the side plates 13. Are arranged as follows.
The bottom plate 12 has a smoke exhaust hole 14 penetrating therethrough, and a gap formed between the other surface 12b of the bottom plate 12 and the one surface 20a of the printed circuit board 20 (hereinafter referred to as a “smoke exhaust path”). ) 70 communicates with the outside.

The predetermined side plate 13a of the side plates 13 is provided with a light emitting element 40 that emits near-infrared light having an optical axis 41 substantially parallel to one surface 12a of the bottom plate 12 and directed toward the center of the dark room 60. (To be precise, the optical axis 41 of the light emitting element 40 is substantially parallel to the one surface 12a of the bottom plate 12 and coincides with a straight line toward the center of the dark room 60).
A ground pattern for shielding electrical noise is provided on the other surface 20b of the printed circuit board 20 that does not face the other surface 12b of the bottom plate 12. The light receiving element 50 is scattered at the position of the substrate hole 21 on the ground pattern. It is mounted so that it can receive light.

That is, a dark room 60 that prevents inflow of outside light while allowing inflow of smoke is formed by the side plate 13 that forms a discontinuous annular labyrinth with the bottom plate 12 and the optical bench cover 30.
The light receiving element 50 senses light from the dark room 60 (precisely, it is scattered light from smoke and is included in the detection wavelength 800 to 1000 nm), and its optical axis 51 is connected to the substrate hole 21 and the optical element. It is formed by passing through the base hole 11 and intersects the optical axis 41 of the light emitting element 40 with an obtuse angle (approximately 120 °).

Therefore, the photoelectric smoke detector 100 is installed so that the printed circuit board 20 is on the ceiling side or the wall side of the building, and the generated smoke passes through the gap (the labyrinth is formed) between the side plates 13 and is in the dark room 60. It flows into the smoke exhaust passage 70 through the bottom plate 12 and the optical platform hole 11, enters the smoke exhaust passage 70, and flows out of the photoelectric smoke detector 100.
At this time, since the light emitted from the light emitting element 40 is scattered by the smoke in the dark room 60, the scattered light is detected by the light receiving element 50.

The relationship between the angle formed by the optical axis of the light emitting element and the optical axis of the light receiving element and the scattered light output sensed by the light receiving element was measured.
As a result, the scattered light output increases as the angle formed by the optical axes is larger than 90 °, and particularly when the angle exceeds 110 °, the scattered light output increases rapidly.
Accordingly, since the photoelectric smoke detector 100 has an angle formed by the optical axis 41 and the optical axis 51 of approximately 120 °, it is possible to detect more scattered light and improve the S / N ratio. Yes.

In addition, a ground pattern that shields electrical noise is provided on the other surface 20b that does not face the bottom plate 12 of the printed circuit board 20, and the light receiving element 50 is mounted on the ground pattern. Since it is not necessary to store in a shielding case for shielding, the number of parts is reduced and the manufacturing cost is reduced.
Furthermore, since the dark room 60 is formed by the plurality of side plates 13 that form a discontinuous annular labyrinth with the bottom plate 12 and the optical bench cover 30, and there is no barrier that inhibits the inflow of smoke from a specific direction, all directions Thus, smoke does not flow into the dark room 60 and the inflow (directivity) does not deteriorate.

[Embodiment 2]
Next, a photoelectric smoke detector according to Embodiment 2 of the present invention will be described with reference to the drawings. In addition, the same code | symbol is attached | subjected to the part which is the same as that of Embodiment 1, or an equivalent part, and one part description is abbreviate | omitted.
7 to 9 illustrate a photoelectric smoke detector according to the second embodiment of the present invention. FIG. 7 is a plan view, FIG. 8 is a perspective view showing members separated, and FIG. 9 is a side view. FIG.

7 to 9, the photoelectric smoke detector 200 changes the installation position of the light receiving element 50 in the photoelectric smoke detector 100 described in the first embodiment, and the substrate changes with the change of the installation position. The hole 21 and the ground pattern are removed, and the light receiving element 50 is housed in a shield case 53 in which a case hole 52 is formed.
That is, the light receiving element 50 is mounted on one surface 20a facing the other surface 12b of the bottom plate 12 of the printed circuit board 20, and the light receiving element 50 is housed in a shield case 53 that shields electrical noise.

Therefore, the light receiving element 50 senses the scattered light that has passed through the optical base hole 11 formed in the bottom plate 12 and the case hole 52 formed in the shield case 53 on the one surface 20a side of the printed circuit board 20 on the bottom plate 12 side. .
Since the optical axis 41 of the light emitting element 40 and the optical axis 51 of the light receiving element 50 intersect with an obtuse angle (approximately 120 °), as in the photoelectric smoke detector 100 described in the first embodiment, S / N ratio and inflow are improved.

  As described above, since the S / N (signal / noise) ratio is improved, the photoelectric smoke detector according to the present invention can be widely used as various photoelectric smoke detectors installed in various places. it can.

10: Optical base, 11: Optical base hole, 12: Bottom plate, 12a: One side, 12b: The other side, 13: Side plate, 13a: Side plate, 14: Smoke vent, 20: Printed circuit board, 20a: One side Surface: 20b: the other surface, 21: substrate hole, 30: optical base cover, 40: light emitting element, 41: optical axis, 50: light receiving element, 51: optical axis, 52: case hole, 53: shield case, 60 : Dark room, 70: flue gas path, 100: photoelectric smoke detector (Embodiment 1), 200: photoelectric smoke detector (Embodiment 2).

Claims (1)

An optical bench comprising: a bottom plate in which a penetrating optical bench hole is formed; and a plurality of side plates that are erected on one surface of the bottom plate and arranged annularly;
An optical stand cover installed at an end of the side plate;
A printed circuit board facing the other surface of the bottom plate at a predetermined interval and having a through-hole formed therein;
Formed by the bottom plate, the plurality of side plates and the optical bench cover, a darkroom in which outside light cannot enter and smoke can flow,
A light emitting element that is installed in the darkroom and emits light having an optical axis substantially parallel to one surface of the bottom plate;
A ground pattern that is provided on a surface that does not face the other surface of the bottom plate of the printed circuit board and shields electrical noise;
A light receiving element that is mounted at the position of the substrate hole on the ground pattern, receives light scattered from smoke particles in the dark room, and is irradiated from the light emitting element;
Have
The optical axis of the light receiving element is formed by penetrating the substrate hole and the optical platform hole, and the optical axis of the light emitting element and the optical axis of the light receiving element intersect at an obtuse angle in the dark room. A photoelectric smoke detector.

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