JPS5941137B2 - light scattering smoke detector - Google Patents

Description

[Detailed description of the invention] This invention relates to a light scattering type smoke detector.

A conventional optical system of a light scattering type smoke detector that detects smoke by receiving light scattered by smoke is shown in FIG.

That is, the light-emitting element A is arranged on the Z-axis of space, the light-receiving element B is arranged on the Y-axis, and the light-emitting element A is caused to emit light. Smoke is Z
When it is not on the axis, the light does not reach the light receiving element B and is not received. C is a light shielding plate arranged parallel to the X-Y axis to prevent malfunctions due to light leakage. On the other hand, when smoke exists on the Z-axis, the smoke particles D cause the smoke to spread in all directions (including the X-axis, Y-axis, and Z-axis).
The light is scattered at a solid angle of 4π), and the light receiving element B receives the scattered light in the Y-axis direction. However, this optical system can only detect a portion of the solid angle φ out of the total scattered light, and even if a condensing lens is added to the light-receiving element B, the difference is only in degree, so the so-called S
This has the disadvantage that the /N ratio (scattered light due to smoke/disturbance noise) is extremely low, and malfunctions are likely to occur.
For this reason, this optical system has problems such as the need to increase the luminous flux of the light emitting element A, which increases power consumption, and the need to increase the gain of signal amplification on the light receiving side, which reduces circuit margin. It was hot. In order to solve this problem, a light scattering type smoke detector, which is the basis of the present invention, is shown in FIGS. 2 to 4, which improves the light reception efficiency of scattered light.

That is, in this light scattering type smoke detector, a printed circuit board 2 is screwed to a base 1 that is attached to a ceiling, etc., and a circuit component 3, a light collecting block 4, a light emitting diode tungsten lamp, a discharge tube, etc. are attached to the printed circuit board 2. Light emitting element 5, photodiode, phototransistor, cadmium C sulfide
A light receiving element 6 such as dS is attached and covered with a front cover 7. The front cover 7 is provided with a smoke intake hole 8 and a light trap 9 made of black foamed urethane or the like that absorbs the light from the light emitting element 5. 10 is a smoke sensitive area.

With this structure, when smoke is generated due to a fire, the smoke enters the sensor through the smoke intake hole 8 of the front cover 7 and enters the smoke sensitive area 1.
When the light reaches 0, the primary light from the light emitting element 5 is scattered by the smoke particles, the scattered light is focused on the light receiving element 6 by the condensing block 4, and the level of the output signal of the light receiving element 6 increases. When the temperature rises above a certain value, the sensor is activated.
Next, the configuration of the optical system will be explained. That is, as shown in FIGS. 3 and 4, a solid cylindrical cylinder is formed using an optically isotropic transparent material such as acrylic resin, styrene resin, polyester resin, or epoxy resin. The first reflector 13 is formed by plating or vapor-depositing aluminum or the like on the condensed surface 13a, thereby forming the condensing block 4. A cylindrical hole 15 is formed with one focal axis 14 of this first reflector 13 as the central axis, and a light-shielding tube 16 having a length of about half the axial length is fitted into the cylindrical hole 15. The light emitting element 5 is mounted inside the cylindrical hole 15.
A smoke sensitive area 10 communicating with the smoke intake hole 8 of the front cover 7 is formed by the portion where the light shielding tube 16 is not located. On the other hand, the first
The other focal axis 18 of the reflector 13 is the first focal axis, and the hyperbolic cylindrical surface 21 having the second focal axis 20 on the long axis 19 of the first reflector 13 is connected to the first reflector 13. The second reflector 22 is formed by notching (molding) and forming a mirror surface on its surface. The light-receiving element 6 is embedded on the second focal axis 20 of the second reflector 22 located within the first reflector 13 so that its light-receiving surface faces the reflective surface of the second reflector 22. . With such a configuration, the primary light emitted from the light emitting element 5, when no smoke enters the smoke sensitive area 10, goes straight and is supplemented by the optical trap 9, and the primary light emitted from the smoke sensitive area 10 is
When smoke enters the interior, it is scattered in all directions, and all of the scattered light on the plane perpendicular to the focal axis 14 forms the cylindrical surface 13a and the hyperbolic cylindrical surface 21 geometrically as shown by the arrow in FIG. The light is reflected and reaches the light receiving element 6. In other words, since the scattered light A in a plane perpendicular to the J focal axis 14 is incident toward the cylindrical surface 13a with one focal axis 14 of the cylindrical surface 13a as the center, the first reflected light A2 is Geometrically the other focal axis 1
Focus the light on 8. On the other hand, the hyperbolic cylinder surface 21 has the focal axis 18 of the hyperbolic cylinder surface 13a as the first focal axis, and the light receiving element 6 as the second focal axis 2.
0, when the first reflected light A2 enters the hyperbolic cylinder surface 21, the second reflected light A3 gathers at the second focal axis 20,
The light enters the light receiving element 6. Therefore, the light-scattering smoke detector using this optical system receives all of the scattered light (angle 2π) perpendicular to the focal axis 14, so compared to the conventional one, The light receiving efficiency can be significantly improved, so S
Since the /N ratio can be increased, the above-mentioned problems can be reduced.

However, in this light-scattering type smoke detector, since the light emitting element 5 emits light to the smoke-sensitive area 10 as diverging light, there is a loss in light reception, and therefore it is necessary to use an optical system such as a lens, which increases the number of parts. Additionally, there is a problem in that assembly becomes complicated and costs increase.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a light-scattering type smoke sensor which can reduce loss of light reception, simplify assembly, and reduce costs.

A first embodiment of this invention is shown in FIG. That is, in this light scattering type smoke detector, a transparent partition plate 23 is formed in the middle part of the cylindrical hole 15' so that the transparent body is continuous. A lens 24 is integrally formed (molding means) on a partition plate 23, and the other configurations are the same as those shown in FIGS. 2 to 4. In this way, the diverging light B, emitted from the light emitting element 5 passes through the lens 24, becomes a convergent light B2, and irradiates the smoke sensitive area 10. Therefore, loss of light reception is reduced, and since the lens 24 is integrally formed, assembly is simple and costs are reduced. A second embodiment of the invention is shown in FIG.

That is, this light scattering type smoke detector has a bottomed cylindrical hole 15I0.
) A concave mirror 25 is formed by forming a convex spherical surface with an optical axis inclined at 45 degrees with respect to the focal axis 14 above the bottom surface and mirroring the surface, and the light emitting element 5 is
The diverging light C1 is incident thereon, and the convergent light C2 is emitted into the smoke sensitive area 10 formed by the bottomed cylindrical hole 15f. Its operation and effect are similar to those of the first embodiment. As a modification of this embodiment, in place of the concave mirror 25, a part of a parabolic mirror of revolution whose main axis is the rotation axis is used, and the light emitting element 5 is positioned at its focal point.
The diverging light beams are converged to obtain a bundle of parallel rays.

In addition, a rotating circular mirror whose long axis is the rotation axis is used, and the light emitting element 5 is located at one focal point, and the smoke sensitive area 10 is located at the other focal point.
, the diverging light is focused at the focal point within the smoke sensitive area 10 without any loss. It should be noted that there are various types of optical systems in addition to the above-mentioned embodiments for the optical system from which the light is reflected from the circular reflection surface until it is focused on the light-receiving element 6.

As described above, in the light scattering type smoke detector of the present invention, the optical system that focuses the diverging light of the light emitting element onto the smoke sensitive area is integrally formed in the transparent body of the condensing block. It has the effect of being easy to assemble and reducing costs.

[Brief explanation of the drawing]

Figure 1 is a diagram of the principle of the optical system of a conventional light-scattering smoke detector, Figure 2 is a vertical cross-sectional view of the light-scattering smoke detector that is the basis of this invention, and Figure 3 is a cross-section of its light-concentrating block. 4 is a cross-sectional view thereof, FIG. 5 is a cross-sectional view of a light concentrating block according to a first embodiment of the present invention, and FIG. 6 is a cross-sectional view of a light concentrating block according to a second embodiment of the present invention. 4... Concentrating block, 5... Light emitting element, 6... Light receiving element, 13a... Cylindrical surface (cylindrical reflection surface), 15''
15″...tube hole, 24...lens, 25...concave mirror.

Claims (1)

[Scope of Claims] 1. A condensing block in which an elliptical reflective surface is formed on the peripheral surface of a transparent body, a smoke-sensing area recessed on one focal axis of this condensing block, and this smoke-sensing area. a light-emitting element that emits diverging light to the transparent body; an optical system that is integrally formed with the transparent body to converge the divergent light of the light-emitting element onto the smoke-sensitive area; and a focal axis of the other condensing block. A light scattering smoke detector equipped with a light receiving section. 2. The light scattering smoke detector according to claim 1, wherein the optical system is a convex lens. 3. The light scattering smoke detector according to claim 1, wherein the optical system is a concave mirror. 4. The light scattering smoke detector according to claim 1, wherein the optical system is a parabolic mirror of revolution. 5. The light scattering smoke detector according to claim 1, wherein the optical system is a rotating circular mirror.