JP5379369B2 - Photoelectric smoke detector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a photoelectric smoke sensor having high smoke detection accuracy. <P>SOLUTION: This photoelectric smoke sensor has: a housing 21 having a plurality of wall parts 23 making smoke from the outside flow in the housing 21 and shielding direct light from the outside; a light emission part 25 irradiating light into the housing 21; a light reception part 26 receiving scattered light of the light by the smoke flowing into the housing 21; and a light shielding wall 27 shielding direct light toward the light reception part 26 from the light emission part 25. The light emission part 25 and the light reception part 26 are provided such that respective optical axes of them cross inside the housing 21, and are provided such that the optical axis of the light reception part 26 is directed to an edge part 27a on the optical axis side of the light emission part 25 of the light shielding wall 27. <P>COPYRIGHT: (C)2009,JPO&amp;INPIT

Description

  The present invention includes a housing having a plurality of wall portions that allow smoke from the outside to flow in and blocks direct light from the outside, a light emitting portion that irradiates light inside the housing, and a flow that flows into the housing. The present invention relates to a photoelectric smoke detector including a light receiving unit that receives scattered light of the light due to smoke and a light shielding wall that blocks direct light from the light emitting unit toward the light receiving unit.

  Conventionally, a photoelectric smoke detector is provided with a light emitting unit that emits light and a light receiving unit that receives light in a smoke detection chamber formed by a housing, and smoke flows into the smoke detection chamber. In addition, the light is scattered by the smoke, and the smoke is detected by detecting the scattered light.

  In such a photoelectric smoke detector, a plurality of labyrinth walls and the like are provided that allow smoke from the outside to pass through the housing but block light from the outside, and direct light directed from the light emitting portion to the light receiving portion is provided in the smoke detection chamber. A light blocking wall for blocking is provided to improve the detection accuracy of scattered light due to smoke in the light receiving unit (see, for example, Patent Document 1).

JP-A-9-231485

  In the conventional photoelectric smoke detector, direct light from the light emitting portion to the light receiving portion can be blocked by a plurality of wall portions provided in the housing and a light shielding wall provided in the smoke detection chamber. However, there is a possibility that a part of the direct light reflected by the wall portion or the light shielding wall reaches the light receiving portion. For this reason, the conventional photoelectric smoke detector has a problem in that the reflected light becomes a noise component in the detection of scattered light because the scattered light itself from the smoke is weak, and the smoke detection accuracy decreases.

  The present invention has been made in view of the above problems, and an object thereof is to provide a photoelectric smoke detector having high smoke detection accuracy.

FEATURES configuration of a photoelectric smoke sensor according to the present invention for achieving the above object, a housing having a plurality of wall portions for blocking direct light from the outside together with flowing a smoke from the outside, the housing A light emitting part that irradiates light inside, a light receiving part that receives the scattered light of the light due to the smoke flowing into the housing, and a light shielding wall that blocks direct light from the light emitting part toward the light receiving part The light emitting portion and the light receiving portion are provided so that their optical axes intersect each other on the light emitting portion side from the center portion inside the housing, and the light axis of the light receiving portion is the center of the light shielding wall. provided to face the edge of the part side, the position of any of the position ranging from the intersection of the optical axis of the light receiving portion and the optical axis of the light emitting portion to the intersection between the rim portion and the optical axis of the light receiving portion Condensing means having a focus on the light receiving section It lies in the fact digits.

In the case where the light emitting part and the light receiving part are provided so that their optical axes intersect each other on the light emitting part side from the center part inside the housing, the present inventors see scattered light from smoke inside the housing from the light receiving part. Focusing on the light intensity at the time, the light intensity in the vicinity of the edge on the center side of the light shielding wall was found to be the highest.

Therefore, as in this configuration, by providing the light receiving portion so that the optical axis faces the edge of the inside of the housing inside the light shielding wall, the intensity of scattered light due to the received smoke is increased. Compared with the photoelectric smoke detector, the S / N ratio in the light receiving unit can be improved, and the smoke detection accuracy can be improved.

Further, according to this configuration, by providing the light collecting unit with the light collecting unit, the intersection between the optical axis of the light emitting unit and the optical axis of the light receiving unit reaches the intersection of the optical axis of the light receiving unit and the edge of the light shielding wall. The focal point is set at one of the positions. Accordingly, it is possible to increase the intensity of the scattered light due to the smoke received, and to reduce the intensity of the reflected light reaching the light receiving portion as a noise component, so that the S / N ratio at the light receiving portion is increased and the smoke detection accuracy is increased. Can be made higher.

Another characteristic configuration of the photoelectric smoke detector according to the present invention includes a housing having a plurality of wall portions that allow smoke from the outside to flow in and block direct light from the outside, and irradiates the inside of the housing with light. A light-emitting unit, a light-receiving unit that receives the scattered light of the light due to the smoke flowing into the housing, and a light-shielding wall that blocks direct light from the light-emitting unit toward the light-receiving unit, The light receiving part is provided so that the respective optical axes intersect the light emitting part side from the central part inside the housing, and the optical axis of the light receiving part is at the edge of the light shielding wall on the central part side. It is in the point that it is set to face.

  Hereinafter, an embodiment of a photoelectric smoke detector according to the present invention will be described with reference to the drawings. Here, the case where this invention is applied to the smoke detection part 2 in the fire alarm 1 is demonstrated.

  As shown in FIG. 3, the fire alarm device 1 according to the present embodiment has a smoke detection unit 2 that detects smoke, an alarm speaker 3 that emits an alarm sound such as a voice or a buzzer, and light from an LED or the like on the front. And an alarm lamp 4 that lights or blinks. When the smoke detector 2 detects smoke, the fire alarm 1 determines, for example, whether the smoke concentration is higher or lower than a preset threshold value. If the smoke concentration exceeds the threshold value, the fire alarm 1 is determined to be a fire. Then, an alarm sound is emitted from the alarm speaker 3 and the alarm lamp 4 is turned on. The fire alarm 1 is provided with an alarm stop button 5, which can be operated to stop an alarm sound from the alarm speaker 3 and turn off the alarm lamp 4. Also, on the back of the fire alarm 1, there are an attachment part (not shown) for fixing the fire alarm 1 to a wall material, a battery storage part (not shown) for storing a battery for driving the fire alarm 1, etc. It is provided.

  As shown in FIG. 1, the smoke detection unit 2 includes a housing 21 having a smoke detection chamber 22 that detects smoke therein. The housing 21 is provided with a plurality of bowl-shaped wall portions 23 so as to surround the smoke detection chamber 22 so that smoke from the outside can flow into the smoke detection chamber 22 while blocking light from the outside. Yes. Further, an insect repellent net 24 made of a wire net or the like is provided outside the wall portion 23 to prevent erroneous detection due to insects entering the smoke detection chamber 22.

  Inside the housing 21 are a light emitting element 25 such as a light emitting diode that irradiates the smoke detection chamber 22 with light such as near infrared rays, and a photodiode as a light receiving portion that receives the light from the smoke detection chamber 22. A light receiving element 26 is provided. Further, a light shielding wall 27 is provided between the light emitting element 25 and the light receiving element 26 so that direct light from the light emitting element 25 toward the light receiving element 26 can be blocked. For this reason, the light receiving element 26 does not normally receive the light emitted from the light emitting element 25, and can receive the scattered light of the light emitted from the light emitting element 25 due to the smoke only when the smoke flows into the smoke detection chamber 22. Become. The smoke detector 2 can detect the presence of smoke by detecting the scattered light.

In the smoke detector 2 of the fire alarm device 1 according to the present embodiment, the optical axis of the light receiving element 26 intersects with the light emitting element 25 on the light emitting element 25 side from the center in the smoke detection chamber 22. And the optical axis of the light receiving element 26 is provided so as to face the edge 27 a of the light shielding wall 27 on the center side of the smoke detection chamber 22 . Of the light shielding wall 27, in the vicinity of the edge 27a on the optical axis side of the light emitting element 25, not only direct light from the light emitting element 25 but also reflected light reflected by the light shielding wall 27 arrives and is scattered by smoke. . For this reason, the intensity of the scattered light due to smoke when viewed from the light receiving element 26 is highest in the direction of the edge portion 27a of the light shielding wall 27 as shown in FIG. Therefore, by arranging the optical axis of the light receiving element 26 so as to face this direction, the intensity of the scattered light received by the light receiving element 25 is increased, the S / N ratio is increased, and the smoke of the smoke detector 2 is increased. Detection accuracy can be increased.

  The light receiving element 26 is provided with a lens 28 as a condensing means. As the lens 28, it is preferable to use a lens having a focal point at any position among the positions from the intersection of the optical axis of the light emitting element 25 and the optical axis of the light receiving element 26 to the edge portion 27 a of the light shielding wall 27. Such a lens 28 is provided to collect the scattered light between the edge 27a of the light shielding wall 27 from the intersection of the optical axis of the light emitting element 25 and the optical axis of the light receiving element 26, and to receive the smoke by the light receiving element 25. In addition to increasing the intensity of the scattered light due to the noise, the intensity of the light reflected by the wall 22 and the like reaching the light receiving element 25 as a noise component can be reduced, so the S / N ratio is increased and the smoke detection accuracy is improved. Can be higher. When a lens having a shallow depth of focus is used as the lens 28, it is at any point of the intersection of the optical axis of the light emitting element 25 and the optical axis of the light receiving element 26 or the edge 27a of the light shielding wall 27. It is more preferable to use one having a focal point. Since the intensity of scattered light is highest at these points, it is possible to efficiently receive scattered light with high intensity by focusing on any of these points. Therefore, the difference in intensity between the scattered light due to the smoke and the reflected light as the noise component becomes larger, so that the S / N ratio can be further increased.

  In addition, about the structure and function of the fire alarm 1 provided with the other smoke detection part 2, it is the same as that of a conventionally well-known fire alarm.

[Another embodiment]
In the above embodiment, the example in which the lens 28 is provided in the light receiving element 26 has been described. However, the lens 28 may not be provided. Even by arranging the light receiving element 26 so that the optical axis faces the edge portion 27a of the light shielding wall 27, the intensity of the scattered light received by the light receiving element 25 becomes higher than the intensity of the reflected light as a noise component. Therefore, the S / N ratio is increased, and the smoke detection accuracy of the smoke detector 2 can be increased.

  In the above embodiment, the case where the photoelectric smoke detector according to the present invention is applied to the wall-mounted fire alarm 1 has been described as an example. However, for example, the photoelectric smoke detector may be applied to a ceiling-mounted fire alarm or the like. it can.

(Example)
Below, the Example using the fire alarm device 1 which concerns on this embodiment is shown, and this invention is demonstrated in detail. However, the present invention is not limited to these examples.

  In the fire alarm device 1 according to the present embodiment, when the lens 28 is not provided on the light receiving element 26 of the smoke detector 2 (Example 1) and when the lens 28 having a focus is provided on the edge portion 27a of the light shielding wall 27 ( With respect to Example 2), the S / N ratio when receiving scattered light from smoke was examined. As a comparative example, when the light receiving element 26 not provided with the lens 28 is arranged so that the optical axis faces the center of the smoke detection chamber 22 as in the conventional case (not toward the edge 27a of the light shielding wall 27). ) Was also examined for the S / N ratio.

As a result, as shown in Table 1, the S / N ratio is improved by directing the optical axis of the light receiving element 25 toward the edge 27a of the light shielding wall 27 as compared with the comparative example, and the S / N ratio is improved by providing the lens 28. It has been found that the N ratio is higher.

  The photoelectric smoke detector according to the present invention can be applied to a smoke sensor that detects smoke, an alarm device that detects smoke and issues an alarm, a measuring device that measures smoke concentration, and the like.

Plan sectional view of the smoke detector according to the present embodiment Graph showing the intensity of light scattered by smoke Schematic diagram of fire alarm according to this embodiment

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Fire alarm 2 Smoke detection part 21 Housing 23 Wall part 25 Light emitting element (light emission part)
26 Light receiving element (light receiving part)
27 Shielding Wall 27a Edge 28 Lens (Condensing means)

Claims (2)

A housing having a plurality of wall portions that allow smoke from the outside to flow in and block direct light from the outside; and
A light emitting unit for irradiating light inside the housing;
A light receiving unit that receives the scattered light of the light caused by smoke flowing into the housing;
A light shielding wall that blocks direct light from the light emitting unit toward the light receiving unit,
The light emitting part and the light receiving part are provided so that their optical axes intersect each other on the light emitting part side from the central part inside the housing, and the optical axis of the light receiving part is on the central part side of the light shielding wall. Oh Ri provided so as to face the edges,
A light collecting unit having a focal point at any one of positions from an intersection of an optical axis of the light emitting unit and an optical axis of the light receiving unit to an intersection of the optical axis of the light receiving unit and the edge; Photoelectric smoke detector provided in the section . A housing having a plurality of wall portions that allow smoke from the outside to flow in and block direct light from the outside; and
A light emitting unit for irradiating light inside the housing;
A light receiving unit that receives the scattered light of the light caused by smoke flowing into the housing;
A light shielding wall that blocks direct light from the light emitting unit toward the light receiving unit,
The light emitting part and the light receiving part are provided so that their optical axes intersect each other on the light emitting part side from the central part inside the housing, and the optical axis of the light receiving part is on the central part side of the light shielding wall. Photoelectric smoke detector provided to face the edge of the .

Images