JP4987515B2 - smoke detector - Google Patents

Description

  The present invention relates to a smoke detector that optically detects contaminants such as smoke floating in the air, and more particularly to a sampling type (suction type) smoke detector.

Conventional smoke detectors include the following (for example, see Patent Document 1).
The light projecting element and the light receiving element are disposed in the optical chamber so that the optical axes intersect with each other, and particles such as smoke and dust are detected in the detection area where the light projecting area of the light projecting element and the light receiving area of the light receiving element overlap. In a light scattering particle detection sensor that detects particles by receiving scattered light of light from a light projecting element, at least a wall surface of an optical chamber facing the front of a light receiving area of the light receiving element faces downward. Light scattering type particle detection sensor formed in

Japanese Patent Laid-Open No. 4-160699

Conventional smoke detectors have the following problems.
(1) In the conventional example, when light from the light projecting element passes through the aperture, diffracted light is generated around the main beam. Since this diffracted light collides with the inner wall surface in the case and is reflected, and the reflected light may be directly received by the light receiving element, accurate fire detection may not be possible.

 (2) In the conventional example, since the wall surface of the optical chamber facing the light receiving region (field of view range) of the light receiving element is directed downward, dirt on the wall surface and adhesion of dust and the like are prevented, and dropped dirt is optically A space is secured to allow accumulation outside the light receiving area of the chamber. However, if such a structure is used, there is a limit to the miniaturization of the optical chamber, and this structure cannot be adopted in a suction type smoke detector that does not allow dirt to stay.

  In view of the above circumstances, an object of the present invention is to attenuate the diffracted light and prevent it from entering the light receiving unit. Another object is to provide a suction type smoke detector in which fine particles other than the smoke particles that have entered the smoke detector section do not stay in the field of view of the light receiving element.

The present invention has a light emitting element, a light receiving element that has a predetermined optical axis angle with the light emitting element, receives light scattered from the light emitting element by smoke particles in the smoke detecting section, and attenuates stray light facing the light emitting element. A smoke detector comprising: a substantially cylindrical optical case provided in a dark box; and a sampling air passage across the smoke detection portion of the optical case; Of the inner wall surface of the smoke portion, a portion within the visual field range of the light receiving element is formed as a smooth surface having a smooth surface that regularly reflects incident light, and a portion outside the visual field range diffusely reflects incident light. It is formed on a rough surface having a rough surface.

The present invention includes a sampling first air passage that crosses the smoke detection portion of the optical case, a second air passage for clean air, a light receiving amplification circuit that amplifies an output signal of the light receiving element, and an amplification signal A And a fire determination unit for determining a fire when the detection level obtained by D conversion is equal to or higher than a threshold value.

  The smoke detector according to the present invention is characterized in that it is partitioned by an aperture that restricts light of the light emitting element. Diffracted light is generated when the light of the light emitting element of the present invention passes through the aperture, and the diffracted light collides with the smooth surface and is reflected outside the field of view of the light receiving unit. It is characterized by being attenuated by colliding with a surface.

  Since the present invention is configured as described above, out of the beam irradiated from the light emitting element, light that collides with a smooth surface within the field of view of the light receiving element is reflected outside the field of view, and the reflected light is reflected in the field of view. It collides with an uneven surface outside the range and is attenuated. For this reason, noise light (diffracted light) is hardly received in the light receiving unit, so that accurate fire detection can be performed.

  The present inventor thought that the noise light is received by the light receiving unit may be influenced by the degree of smoothness of the wall surface of the smoke detecting unit. Therefore, as shown in FIG. 1, when the inner wall surface of the smoke detector is a smooth surface (case 1), as shown in FIG. 2, only the inner wall surface facing the light receiver of the smoke detector is When the entire surface is uneven (case 2), and as shown in FIG. 3, the portion of the smoke detector wall within the field of view of the light receiving portion is a smooth surface and the other portion is an uneven surface ( Case 3) was examined. The smooth surface is not necessarily limited to a glossy mirror surface, but may be any as long as it has a smooth surface that substantially regularly reflects incident light. On the other hand, the uneven surface may be a rough surface that diffusely reflects incident light. Hereinafter, each case will be described.

Case 1 smoke detector:
As shown in FIG. 1, the light emitting part 3 is provided at one end of the substantially cylindrical optical case 1, and the stray light part 5 is provided at the other end. The light emitting unit 3 is provided with a light emitting element 3a having a condenser lens, and the stray light unit 5 is provided with an optical trap 5a for attenuating stray light.

  A smoke detector 7 is provided in the optical case 1, and both ends of the smoke detector 7 are partitioned by apertures 9a and 9b. On the side wall of the smoke detector 7, a sampling air passage (not shown) across the smoke detector 7, a light receiver 10 that receives scattered light, and light from the light emitting element 3 a directly enter the light receiver 10. And a light-shielding plate (not shown) for avoiding this.

  The light receiving unit 10 includes a light receiving element 10a, and the optical axis 10c of the light receiving element 10a is orthogonal to the optical axis 3c (main beam) of the light emitting element 3a. The inner wall surface of the smoke detector 7 is formed on a surface having no irregularities, a so-called smooth surface, over the entire surface.

Next, the operation of this smoke detector will be described.
The light emitted from the light emitting element 3a enters the smoke detector 7 through the through hole of the aperture 9a, and travels straight through the smoke detector 7. The straight traveling light passes through the aperture 9b, reaches the stray light portion 5, and is then attenuated by the optical trap 5a.
At this time, the light is narrowed by the through hole of the aperture 9a to become the main beam B, but diffracted light (noise light) N is generated from the vicinity of the through hole.

  The diffracted light N collides with the inner wall surface in the visual field range (monitoring range) F of the light receiving unit 10 and is reflected, and the reflected light N collides with the aperture 9b located outside the visual field range F and is reflected. The reflected light N collides with and reflects the inner wall surface near the entrance of the light receiving unit 10, and the reflected light collides with the inner wall surface of the light receiving unit 10 and is then received by the light receiving element 10 a. A part of the diffracted light N collides with and reflects the inner wall surface outside the visual field range F, and the reflected light directly enters the light receiving unit 10.

  In this way, the diffracted light (noise light) N collides with the inner wall surface and repeats a plurality of reflections to reach the light receiving unit 10, but the inner wall surface has a smooth incident angle and a reflection angle that are substantially equal. Since it is a surface, noise light cannot be attenuated sufficiently.

Case 2 smoke detector:
2, the same reference numerals as those in FIG. 1 have the same names and functions.
The difference between the smoke detector and the smoke detector of the case 1 is that the portion of the inner wall surface of the smoke detector 7 that faces the light receiver 10 (the portion in the visual field range F and the portion in the vicinity of the visual field range F). Is formed on the uneven surface, and other portions are formed on the smooth surface.

  In this smoke detector, the diffracted light N collides with and reflects the inner wall surface 7a in the visual field range (monitoring range) F of the light receiving unit 10, and the reflected light N collides with the aperture 9b located outside the visual field range F. And reflect. At this time, since the inner wall surface 7a is an uneven surface, the light absorption rate is high and the total reflected energy is small, but the reflected light is diffused. Therefore, a part N1 of the diffused noise light directly reaches the light receiving unit 10. End up. Therefore, the diffracted light N cannot be sufficiently attenuated.

Case 3 smoke detector:
3, the same reference numerals as those in FIG. 1 have the same names and functions.
The difference between the smoke detector and the smoke detector of the case 1 is that, of the inner wall surface of the smoke detector 7, the inner wall surface 7b in the visual field range F of the light receiving unit 10 is formed on a smooth surface, and the other portions. Is formed on the uneven surface.

  In this smoke detector, the diffracted light N collides and reflects on the inner wall surface 7b in the visual field range (monitoring range) F of the light receiving unit 10, and the reflected light N collides with the aperture 9b located outside the visual field range. Reflect. At this time, since the aperture 9b is an uneven surface, the light absorptance is high, and the total reflected energy is small. The diffracted light N is further attenuated because it is repeatedly reflected while being absorbed by the uneven surface.

  A part of the diffracted light generated in the vicinity of the through hole of the aperture 9a also collides with a portion other than the inner wall surface 7b of the visual field range F, that is, an inner wall surface outside the visual field range of the light receiving unit 10, Is an uneven surface, so that light is efficiently absorbed, and even if noise light diffuses, it is sufficiently attenuated before reaching the light receiving unit 10.

As is clear from the above, Case 3 has a greater attenuation of diffracted light and a smaller amount of light entering the light receiving portion than Case 1 and Case 2, so that it is possible to accurately detect a fire or the like.
The present invention has been made on the basis of the above knowledge, and of the inner wall surface of the smoke detection portion of the optical case, the portion within the visual field range of the light receiving element is formed on a smooth surface, and the portion outside the visual field range Is characterized by being formed on an uneven surface.

An embodiment of the present invention will be described with reference to FIGS.
A light emitting unit 3 is provided at one end of the substantially cylindrical optical case 1, and a stray light unit 5 is provided at the other end. The light emitting unit 3 is provided with a light emitting element 3a having a condenser lens, and the stray light unit 5 is provided with an optical trap 5a for attenuating stray light.

  A smoke detector 7 is provided in the optical case 1, and both ends of the smoke detector 7 are partitioned by apertures 9a and 9b. On the side wall of the smoke detector 7, the sampling air passage 14 that crosses the smoke detector 7, the light receiver 10 that receives scattered light, and the light from the light emitting element 3 a do not enter the light receiver 10 directly. And a light shielding plate (not shown).

  The sampling air passage 14 includes a sampling pipe 16 that sucks sampling air SA into the smoke detecting section by the rotation of the fan 15, and an exhaust pipe 17 that faces the sampling pipe 16 with a passage interval. Yes.

  A coarse filter 18 is provided at the tip of the sampling tube 16, and a cylindrical fine filter 19 having a finer mesh is erected on the outer periphery of the coarse filter 18. A clean air passage (second air passage) 21 surrounding a sampling passage (first air passage) 20 is formed between the fine filter 19 and the exhaust pipe 17.

  The light receiving unit 10 includes a light receiving element 10a, and the optical axis 10c of the light receiving element 10a intersects the optical axis 3c (main beam) of the light emitting element 3a at a predetermined angle.

  Of the inner wall surface of the smoke detector 7, the inner wall surface 7 b in the visual field range (monitoring range) F of the light receiving unit 10 is formed as a smooth surface, and the other part is formed as an uneven surface.

Next, the operation of this embodiment will be described.
When the fan 15 is rotated, the sampling air SA is sucked into the smoke detector 7 from the sampling pipe 16, and the sucked sampling air SA passes through the coarse filter 18 and the sampling air from which large foreign matters such as dust are removed. It becomes SA1.

  The sampling air SA1 is sucked into the exhaust pipe 17 through the sampling air passage (first air passage) 20, and a part of the sampling air SA1 is filtered through the fine filter 19 to become clean air SA2. . The clean air SA2 travels through the clean air passage 21 so as to surround the sampling air SA1, and is sucked into the exhaust pipe 17.

  Light emitted from the light emitting element 3a of the light emitting unit 3 enters the smoke detecting unit 7 through the through hole of the aperture 9a, travels straight through the smoke detecting unit 7, passes through the aperture 9b, and enters the stray light unit 5. And is attenuated by the optical trap 5a.

  When the light (main beam) passes through the smoke detector 7, if smoke particles are present in the sampling air SA1 introduced from the air passage 14, scattered light is generated and the scattered light is received. The light is received by the unit 10. When the scattered light is received by the light receiving unit 10, the output signal of the light receiving element 10a is amplified by a light receiving amplifier circuit (not shown), A / D converted, and output to the fire determining unit. When the output level is equal to or higher than the threshold, the fire determination unit determines that a fire has occurred and issues an alarm or the like.

  When the light from the light emitting element 3a passes through the aperture 9a, diffracted light (noise light) N is generated. This diffracted light N is generated by the inner wall surface 7b in the visual field range (monitoring range) F of the light receiving unit 10. The reflected light N collides with the aperture 9b located outside the visual field range F and is reflected. At this time, since the aperture 9b is an uneven surface, the light absorptance is high, and the total reflected energy is small. Since the diffracted light N is repeatedly reflected while being absorbed by the uneven surface, it is greatly attenuated.

  A part of the diffracted light N generated in the vicinity of the through hole of the aperture 9a also collides with a portion other than the inner wall surface 7b of the visual field range F, that is, an inner wall surface outside the visual field range of the light receiving unit 10, Since the portion is a concavo-convex surface, light is efficiently absorbed, and even if noise light diffuses, it is sufficiently attenuated before reaching the light receiving unit 10.

6 is a longitudinal sectional view showing a comparative example 1. FIG. 10 is a longitudinal sectional view showing a comparative example 2. FIG. It is a longitudinal section showing an embodiment of the invention. It is a longitudinal cross-sectional view which shows the Example of this invention. It is an enlarged view which shows an air passage. It is a block diagram which shows the suction | inhalation of sampling air, and the flow path of exhaust_gas | exhaustion.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Optical case 3 Light emission part 5 Stray light part 7 Smoke detection part 9a Aperture 9b Aperture 10 Light receiving part 14 Air path F Light receiving part visual field range N Diffracted light (noise light)
SA sampling air

Claims (4)

A light-emitting element, a light-receiving element that has a predetermined optical axis angle with the light-emitting element and receives scattered light of the light-emitting element due to smoke particles in the smoke detector, and an optical trap that attenuates stray light facing the light-emitting element In a smoke detector comprising: a substantially cylindrical optical case provided in a dark box; and a sampling air passage across the smoke detection portion of the optical case;
Of the inner wall surface of the smoke detection section of the optical case, the portion within the visual field range of the light receiving element is formed as a smooth surface having a smooth surface that regularly reflects incident light, and the portion outside the visual field range is incident. A smoke detector having a rough surface having a rough surface for diffusely reflecting light .   A first air passage for sampling across the smoke detection section of the optical case, a second air passage for clean air, a light receiving amplification circuit for amplifying the output signal of the light receiving element, and A / D conversion of the amplified signal The smoke detector according to claim 1, further comprising a fire determination unit that detects a fire when a detection level is equal to or higher than a threshold value.   The smoke detector according to claim 1, wherein the smoke detector is partitioned by an aperture that restricts light of the light emitting element.   Diffracted light is generated when light from the light emitting element passes through the aperture, the diffracted light collides with the smooth surface and is reflected outside the field of view of the light receiving unit, and the reflected light collides with the uneven surface. 4. The smoke detector according to claim 1, wherein the smoke detector is attenuated.

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