JPH08263767A - Particulate detecting sensor - Google Patents

Abstract

PURPOSE: To provide a particulate detecting sensor having a high SN ratio, long service life, an inexpensive price, and high sensitivity and capable of suppressing the generation of damage. CONSTITUTION: Air sucked into a suction port 1 is turned to a laminar flow with a low flow rate in a suction side air room 2, allowed to flow from a suction side nozzle 3 into a smoke detection part while forming a passage having a slit-like cross sectional shape, sucked to an exhaust side nozzle 4, and discharged to an exhaust port 6 through an exhaust side air room 5. The scattered light of light emitted from a light emitting element 7a which is generated due to particulates such as smoke flowing into the smoke detection part is received by a light receiving element 8a, so that the particulates can be detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a fine particle detection sensor for detecting fine particles such as smoke generated during a fire or dust contained in the air, and in particular, the presence of fine particles can be detected by detecting scattered light from the fine particles. The present invention relates to a photoelectric type particle detection sensor for detecting.

[0002]

2. Description of the Related Art Conventionally, in smoke detectors as an example of this type of particulate matter detection sensor, a large amount of light source such as a discharge tube or a laser is used, or a photomultiplier tube, an avalanche photodiode, etc. The high-sensitivity light-receiving element was used to obtain high sensitivity. Further, by using a light source with a large amount of light and a light receiving element with high sensitivity in combination, or by bringing the light receiving element or its optical system close to the smoke detecting section, fine particle detection with higher sensitivity has been performed.

[0003]

However, the problem of deterioration of light quantity due to blackening of the discharge tube and deterioration of light absorption due to light absorption at the crystal facet of the semiconductor laser has not been solved yet. Similarly, the photomultiplier tube and avalanche photo Since the diode requires a high-voltage power supply, there is a problem of deterioration of the electrolytic capacitor in the booster circuit in the power supply device, and there has been a problem of extending the life of the device. Further, there is a problem that not only these elements themselves are expensive, but also peripheral circuits such as a power supply circuit and a cooling device are complicated, so that the entire apparatus is expensive. Furthermore, in the case of a sensor in which the light receiving element or its optical system is brought close to the smoke detecting section in order to increase the amount of received light,
There is also a problem that the flow path of smoke becomes narrow, a sufficient amount of smoke inflow cannot be secured, and the light receiving element is contaminated by being exposed to smoke, which is a combustion product. It should be noted that, in a fine particle detection sensor of general sensitivity, a long-life and inexpensive element such as a light-emitting diode or a photodiode is used, but a decrease in S / N ratio due to the directional characteristic of the light-emitting element is reduced. Due to restrictions such as the amount of light emission and the light receiving sensitivity, it has not been possible to realize a sensor having high sensitivity that can detect smoke diluted by the air conditioner.

The present invention has been made in order to solve the above problems, and provides a fine particle detection sensor having a high S / N ratio, being less likely to be contaminated, having a long life, being inexpensive, and having high sensitivity. With the goal.

[0005]

According to a first aspect of the present invention, there is provided a fine particle detection sensor in which a light emitting element and a light receiving element are arranged so as to sandwich a smoke detecting section with a predetermined angle offset from the facing position and flow into the smoke detecting section. In a scattered light smoke detector that detects smoke by receiving scattered light from the light emitting element due to smoke with a light receiving element, a slit-shaped suction side nozzle and a suction side nozzle arranged so as to face the smoke detection section. And a slit-shaped exhaust-side nozzle disposed so as to face the smoke-detecting section, and forming a slit-shaped smoke flow path from the suction-side nozzle through the smoke-detecting section to the exhaust-side nozzle. It is a thing.

According to a second aspect of the present invention, in the sensor of the first aspect, the suction side air chamber and the exhaust side air chamber are connected to the suction side nozzle and the exhaust side nozzle, respectively. The particle detection sensor according to claim 3,
The sensor according to claim 1 or 2, wherein the light emitting element comprises a plurality of LEDs.

The particle detection sensor according to claim 4 is the sensor according to any one of claims 1 to 3, wherein the light from the light emitting element which is installed facing the light emitting element and which has passed through the smoke detecting portion is A first optical trap portion for preventing the reflected light from returning to the smoke detecting portion, and a first light trap portion for facing the light receiving element and for preventing the light reflected in the smoke detecting portion from directly entering the light receiving element. And two optical trap portions.
The particle detection sensor according to claim 5 is the sensor according to any one of claims 1 to 4, wherein the first light blocking member prevents the light incident from the light emitting element to the light receiving element on the outer wall surface of the suction side nozzle. Is used as. A fine particle detection sensor according to a sixth aspect is the sensor according to the fourth or fifth aspect, wherein the light leaking from the outer wall surface of the exhaust side nozzle from the first light trap portion is prevented from directly entering the second light trap portion. Second
It is used as a light-shielding member. The fine particle detection sensor according to claim 7 is the sensor according to any one of claims 2 to 6, wherein light from the light emitting element is reflected by the tip of the suction side nozzle and directly enters the second light trap portion. A third light shielding member for preventing this is provided on the outer wall surface of the suction side nozzle on the light emitting element side.

The fine particle detection sensor according to claim 8 is the sensor according to any one of claims 1 to 7, wherein the scattered light of the light emitted from the light emitting element in the smoke detector is reflected and received by the light receiving element. The reflecting mirror is provided so as to face the light receiving element.

According to a ninth aspect of the present invention, there is provided a fine particle detection sensor in which a light emitting element and a light receiving element are arranged with a predetermined angle offset from each other so as to sandwich the smoke detecting section, and the smoke which flows into the smoke detecting section is generated during a fire. Alternatively, in a fine particle detection sensor for detecting fine particles such as dust contained in air, a light shielding body for preventing direct light from the light emitting element from entering the light receiving element is provided between the light emitting element and the light receiving element. Is arranged in the flow path of the sucked air.

[0010]

In the fine particle detection sensor according to claim 1,
A smoke channel with a slit-shaped cross section is formed from the slit-shaped suction side nozzle through the smoke detector to the slit-shaped exhaust side nozzle, and the scattered light from the light emitting element due to the smoke in this smoke channel is received. The light is received by the element. Since the air sucked from the monitoring space is guided to the smoke detection section by the slit-shaped suction side nozzle, it is possible to draw an appropriate amount of air (a lot or a few) into the smoke detection section when detecting smoke and the like. Therefore, as compared with the case where a large amount of air is sucked, the light source system of the light emitting element or the light receiving element is not contaminated by smoke, and thus the distance between the smoke detecting section and the light source system can be shortened. Further, in the case where the nozzle diameter is made small and air is sucked in even further, the nozzle is not clogged with dust or the like.

In the fine particle detection sensor according to the second aspect, when the fine particles are present in the air sucked by the suction side air chamber having a large flow passage cross section, the fine particles are diffused and homogenized in the air chamber. It will be reliably detected in the smoke section. Further, foreign matter having a high sedimentation velocity that has entered the air is sedimented and adhered in the suction side air chamber and is prevented from entering the smoke detecting portion. In the fine particle detection sensor according to the third aspect, the plurality of light emitting elements are provided, and the sensitivity can be increased by increasing the amount of emitted light, and it is possible to cover that less air is sucked into the smoke detecting section. In addition, by arranging a plurality of light emitting elements in parallel to form a slit-like optical path for the slit-shaped smoke, or by disposing a plurality of light-emitting elements so that the light is condensed for the slit-like smoke. If arranged, the sensitivity will be further enhanced.

In the particle detection sensor according to claim 4, the first and second optical trap portions prevent stray light from entering the light receiving element, and in the particle detection sensor according to claim 5, the outer wall surface of the suction side nozzle is The first light blocking member prevents light from directly entering the light receiving element from the light emitting element, and in the particle detection sensor according to claim 6, the outer wall surface of the exhaust side nozzle serves as the second light blocking member from the first light trap portion. The leakage light is prevented from directly entering the second light trap portion, and in the particle detection sensor according to claim 7, the third light shielding member provided on the outer wall surface of the suction side nozzle on the light emitting element side emits light. It is possible to prevent the light from the element from being reflected by the tip of the suction side nozzle and directly entering the second light trap portion, so that the S / N ratio can be improved. Since the light trap portion is devised as described above, even if the amount of emitted light is increased by using a plurality of LEDs, noise components such as stray light due to reflection on the inner wall surface will not increase.

According to an eighth aspect of the present invention, there is provided the particle detection sensor according to any one of the first to sixth aspects, wherein a reflecting mirror provided facing the light receiving element reflects scattered light generated in the smoke detecting section. Light to the light receiving element. This improves the sensitivity of the smoke detector.

In the fine particle detection sensor according to the ninth aspect, a light shield for preventing the direct light of the light emitting element from entering the light receiving element is arranged in the air flow path. In the conventional particulate sensor, when moisture such as dew is attached to the tip of the light shield, the light from the light emitting element may hit the water and the light may be directly incident on the light receiving element. Since the light shield is provided in the air flow path, it is possible to prevent moisture from adhering to the light shield due to the air flow. The light shield is
The suction side nozzle or the exhaust side nozzle can also be used. This simplifies the structure.

[0015]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Example 1. 1 is a plan sectional view showing a particle detection sensor according to Embodiment 1 of the present invention. The suction side air chamber 2 is connected to the suction port 1, and the suction side nozzle 3 is connected to the suction side air chamber 2. An exhaust side nozzle 4 is arranged so as to face the suction side nozzle 3, and an exhaust port 6 is connected to the exhaust side nozzle 4 via an exhaust side air chamber 5. The suction side nozzle 3 and the exhaust side nozzle 4 each have a slit-shaped nozzle hole of the same shape extending in a direction perpendicular to the paper surface, and the space between the suction side nozzle 3 and the exhaust side nozzle 4 is The smoke contained in the air is irradiated with light from a light emitting unit 7 described later to form a smoke detecting unit that emits scattered light.

The light emitting portion 7 is arranged so as to face the smoke detecting portion, while the light receiving portion 8 is arranged so as to be displaced by a predetermined angle from the facing position of the light emitting portion 7 which sandwiches the smoke detecting portion. Further, this sensor includes a first optical trap portion 9 arranged to face the light emitting portion 7 and a second optical trap portion 10 arranged to face the light receiving portion 8.

When an air sampling pipe (not shown) opening in the monitoring space is connected to the suction port 1 and a suction fan (not shown) is connected to the exhaust port 6 to drive the suction fan,
The air in the monitoring space is sucked by negative pressure through the air sampling pipe, introduced into the smoke detector through the suction port 1, the suction side air chamber 2, and the suction side nozzle 3, and further, the exhaust side nozzle 4 and the exhaust side air. It is discharged through the chamber 5 and the exhaust port 6. At this time, part of the light L1 emitted from the light emitting element 7a of the light emitting unit 7 is scattered by the smoke particles contained in the introduced air, and the scattered light L2 enters the light receiving element 8a of the light receiving unit 8. Most of the light L1 emitted from the light emitting element 7a passes through the smoke detecting section and travels straight, but the transmitted light L3 is attenuated while being repeatedly reflected on the wall surface of the first light trap section 9. A part of the light L4 returning from the light trap portion 9 toward the smoke detecting portion is reflected by the wall surface of the exhaust side nozzle 4 and is introduced again into the first light trap portion 9 to form a labyrinth structure. Furthermore, the light leaked from this maze structure to the smoke detector is
The structure is such that the light is repeatedly reflected on the wall surface of the second optical trap portion 10 and attenuates, and does not enter the light receiving portion 8.

Here, the suction side nozzle 3 is positioned so as to be interposed between the light emitting portion 7 and the light receiving portion 8, and the outer wall surface of the suction side nozzle 3 serves as a first light shielding member from the light emitting element 7a to the light receiving element 8a. It prevents the direct incidence of light. Further, the outer wall surface of the exhaust side nozzle 4 serves as a second light shielding member and prevents the light L4 leaking from the first light trap portion 9 from directly entering the second light trap portion 10. Further, a third light shielding member 3a is provided so as to project on the outer wall surface of the suction side nozzle 3 on the side of the light emitting element 7a, and the light from the light emitting element 7a is reflected by the tip of the suction side nozzle 3 to generate the second light. It prevents the light from directly entering the trap portion 10. In this way, since the suction side nozzle 3 and the exhaust side nozzle 4 are each a light-shielding body that prevents the direct reception of light from the light emitting section 7 into the light receiving section 8, the suction side nozzle 3 and the exhaust side nozzle 4 are caused by the air flow. Water such as dew is prevented from adhering to the tip of the side nozzle 4, and reflected light or the like due to water is prevented from entering the light receiving unit 8.

Next, the flow of air in the particle detection sensor of this embodiment will be described with reference to FIGS. Due to the negative pressure generated by the suction fan connected to the exhaust port 6, the air in the monitoring space is sucked by the air sampling tube and introduced into the suction port 1. After that, the air that has entered the suction side air chamber 2 having a large flow passage cross section becomes a laminar flow having a low flow velocity, and if there is smoke in the air, the smoke becomes homogeneous due to diffusion. Foreign matter having a high sedimentation velocity that has entered the air is sedimented and adhered in the suction side air chamber 2 and is prevented from entering the smoke detecting portion. Next, the air is guided to the suction side nozzle 3 having a long flow passage cross-section, the flow velocity is increased, and a slit-shaped cross section is formed to reach from the nozzle hole of the suction side nozzle 3 to the smoke detecting portion. Here, the cross-sectional shape of the airflow is set to be slit-shaped because the smoke (air) flow path is narrowed in order to prevent the light emitting part 7 and the light receiving part 8 from being contaminated by smoke particles. The smoke flow path is slightly separated from the portion 8, and the height of the smoke flow path is increased for the purpose of preventing pressure loss due to the decrease of the flow path cross-sectional area, and also the reduction of the flow rate is prevented. However, it is also for preventing dust from clogging the nozzle. Since the air having the slit-shaped cross section is sucked by the exhaust side nozzle 4 having the nozzle hole of the same shape as the suction side nozzle 3, the light emitting section 7, the light receiving section 8, the first and second optical trap sections which are blind alleys. It does not reach 9 and 10 and does not stain them. The air chamber 5 on the exhaust side is provided for the purpose of uniformly exhausting the air from the nozzle 4 on the exhaust side because the air sucked and exhausted by the suction fan provided in the subsequent stage of the exhaust port 6 has a negative pressure.

The operation of the first light blocking member formed of the outer wall surface of the suction side nozzle 3 and the third light blocking member 3a provided on the outer wall surface will be described with reference to FIG. The light L1 emitted from the light emitting unit 7 includes not only the main beam L1a and the leaked light L1b but also the edge 7 of the slit at the tip of the light emitting unit 7.
The edge 8b of the slit at the tip of the light receiving portion 8 after being reflected by b
It includes the noise light L1c directed toward. Therefore, as shown in FIG. 4, the noise light L1c can be shielded or attenuated by arranging the tip portion 3b of the suction side nozzle 3 between the noise light L1c and the main beam L1a. Further, the light that is about to leak from the edge of the tip portion 3b of the suction side nozzle 3 toward the edge 8b of the slit of the tip portion of the light receiving portion 8 is shielded or attenuated by the other tip portion 3c of the suction side nozzle 3, The structure is such that it does not enter the light receiving portion 8.

The leakage light L1 emitted from the light emitting section 7
When b is reflected by the tip portion 3b of the suction side nozzle 3, the reflected light passes through the visual field of the light receiving portion 8 and the second optical trap portion 1
It may be incident on 0. Therefore, as shown in FIG. 4, the light emitting section 7 is provided on the outer wall surface of the suction side nozzle 3 on the light emitting section 7 side.
The third light blocking member 3a that is slightly inclined to the light emitting portion 7 side with respect to the central axis of the light L1 emitted from the light emitting portion 7 is provided, and the tip of this third light blocking member 3a is provided at the main beam from the light emitting portion 7. L
Since the leak light L1b emitted from the light emitting unit 7 is configured to come into contact with the tip 1a of the suction side nozzle 3,
It is possible to prevent the light from being reflected by and going toward the second optical trap portion 10.

Example 2. In the first embodiment, instead of the light emitting unit 7, as shown in FIG.
It is also possible to use the light emitting section 17 in which the light emitting section 17 is arranged on the circumference of a circle equidistant from the center of the smoke detecting section so as to collect light at the center of the smoke detecting section. The luminous fluxes emitted from the individual light emitting elements 17a intersect and overlap at the center of the smoke detector (that is, overlap with the air flow path), and the amount of incident light at this portion is increased. As each light emitting element 17a, an LED having a dull directivity due to a condenser lens is used. This type of LED emits not only the required radiation to the front of the LED but also unnecessary light that becomes a noise source to the surroundings because it is not a point light source and the lens has aberrations. Therefore, a pinhole 17b is provided immediately before each LED, and unnecessary radiation is shielded via a plurality of slits 17c.

Further, in the light emitting section shown in FIG. 5, instead of the light emitting element 17a composed of an LED having a condenser lens, as shown in FIG. It is also possible to use the light emitting element 27a composed of an LED having directivity in a wide range. The reflecting mirror 27b is arranged behind the LED, and the LED is arranged at the focal position of the reflecting mirror 27b so as to face the reflecting mirror 27b. As shown in FIG. 7, if a sufficiently large reflecting mirror 27b is used for the light emitting element 27a, a light beam close to parallel light can be obtained, and the pinhole 1 as used in the light receiving unit 17 in FIG.
It becomes possible to remove 7b and the slit 17c.

Example 3. As shown in FIG. 8, using a light emitting section 37 in which a plurality of light emitting elements 37a are linearly arranged,
The slit-shaped light may be radiated to the intersection of the slit-shaped smoke passage formed by the suction-side nozzle 3 and the exhaust-side nozzle 4, that is, the linear smoke-detecting portion. The light emitted from each of the light emitting elements 37a is distributed and scattered in the linear smoke detecting section, and the scattered light is superposed upon entering the light receiving section 8 to increase the amount of received light. Each light emitting element 3
An LED having a dull directivity due to a condenser lens is used as 7a. As described in the second embodiment, this type of LED is not only a required radiation to the front of the LED but also an unnecessary and noise source due to the fact that it is not a point light source or the lens has aberrations. Since light is emitted to the periphery, a pinhole 37b is provided immediately before each LED, and unnecessary radiation is shielded via a plurality of slits 37c.

Further, in the light emitting portion shown in FIG. 8, instead of the light emitting element 37a formed of an LED having a condenser lens, as shown in FIG. It is also possible to use the light emitting element 47a composed of an LED having directivity in a wide range. The reflecting mirror 47b is arranged behind the LED, and the LED is arranged at the focal position of the reflecting mirror 47b so as to face the reflecting mirror 47b. Similar to the light emitting element 27a and the reflecting mirror 27b shown in FIG. 7, if a sufficiently large reflecting mirror 47b is used for the light emitting element 47a, a light beam close to parallel light can be obtained. The pinhole 37b and the slit 37 which looked like
It becomes possible to delete c.

Example 4. It is preferable to use a light receiving unit having a visual field corresponding to the shape of the scattering region in the smoke detecting unit.
The light receiving section 18 shown in FIG. 10 has a spot-like field of view and is used corresponding to the light emitting section of the second embodiment shown in FIG. 5 or 6. Spot-like scattering area E1
The scattered light emitted from the lens 1 passes through the slit 18b and the lens 1
It is incident on 8c. At this time, noise light generated from areas other than the scattering area E1 is blocked or attenuated by the slit 18b. The light that has entered the lens 18c is condensed, and the diaphragm 18d
The light is incident on the light receiving element 18a arranged near the focal point of the lens 18c via. The noise light that has entered the lens 18c is blocked or attenuated by the diaphragm 18d, and only the necessary scattered light enters the light receiving element 18a.

Further, the light receiving section 28 shown in FIG. 11 has a linear field of view and is used corresponding to the light emitting section of the third embodiment shown in FIG. 8 or 9. Lens 2
As 8c, a cylindrical lens or a rod lens that collects light in only one direction is used, and the scattered light emitted from the linear scattering region E2 is collected. The light receiving element 28a is arranged in front of the focal point of the lens 28c to obtain a wide field of view corresponding to the linear scattering region E2. The noise light generated from areas other than the scattering area E2 is shielded or attenuated by the slit 28b, and the noise light entering the lens 28c is refracted by the lens 28c and is expelled to the outside of the light receiving area of the light receiving element, so that only the necessary scattered light is received. To be done.

Example 5. FIG. 12 shows a particle detection sensor according to the fifth embodiment. This sensor is the same as the sensor of the first embodiment shown in FIG. 1 except that a reflecting mirror 20 is installed facing the light receiving unit 8. According to this structure, of the scattered light generated in the smoke detector, not only the scattered light traveling toward the light receiving portion 8 but also the scattered light traveling toward the reflecting mirror 20 in the direction opposite to the light receiving portion 8 is reflected by the reflecting mirror 20. The light is then received by the light receiving element 8a of the light receiving unit 8. Therefore, the amount of received light is increased, and the smoke detection sensitivity is improved. The reflecting mirror 20 may be an elliptical mirror made of a material having a high reflectance such as Ag or Al.

In each of the above-mentioned embodiments, an example in which the present invention is applied to an air sampling type sensor for detecting smoke by introducing the air sucked from the monitoring space through the air sampling tube has been described. The present invention can be similarly applied to a spot type sensor in which smoke naturally flows due to a flow or convection. Further, in each of the above-described embodiments, the example in which the present invention is applied to the detection of smoke generated during a fire is described, but the present invention is similarly applied to a sensor for detecting fine particles such as dust contained in the air. be able to.

[0030]

As described above, in the particulate matter detection sensor according to the present invention, the light emitting element and the light receiving element are arranged so as to be sandwiched by the smoke detecting section and are displaced from each other by a predetermined angle, and the smoke detecting section is flown into the smoke detecting section. In a scattered light smoke detector that detects smoke by receiving scattered light from the light emitting element due to smoke with a light receiving element, a slit-shaped suction side nozzle and a suction side nozzle arranged so as to face the smoke detection section. And a slit-shaped exhaust-side nozzle disposed so as to face the smoke-detecting section, and forming a slit-shaped smoke flow path from the suction-side nozzle through the smoke-detecting section to the exhaust-side nozzle. Therefore, it is possible to obtain a fine particle detection sensor having a high S / N ratio, being less likely to be contaminated, having a long life, being inexpensive, and having high sensitivity.

If the suction side air chamber and the exhaust side air chamber are connected to the suction side nozzle and the exhaust side nozzle, respectively, the fine particles are diffused and homogenized in the suction side air chamber, so that the smoke detecting section can surely generate the fine particles. Detection can be performed. Further, if the light emitting element is composed of a plurality of LEDs, the sensitivity of particle detection is improved.

Opposed to the light emitting element and the first light trap portion for preventing the light from the light emitting element transmitted through the smoke detecting portion from returning to the smoke detecting portion and the light receiving element. And a second light trap portion for preventing the light reflected in the smoke detector from directly entering the light receiving element, the stray light is prevented from entering the light receiving element and the S / N ratio is improved. The ratio can be improved. Further, the outer wall surface of the exhaust side nozzle, which also serves as the first light shielding member for preventing the direct incidence of light from the light emitting element to the light receiving element on the outer wall surface of the suction side nozzle, is
Also serves as a second light-shielding member that prevents the light leaking from the light trap portion from directly entering the second light trap portion, or the light from the light emitting element is reflected at the tip of the suction side nozzle and the second light A high S / N ratio can be obtained by providing a third light shielding member on the outer wall surface of the suction side nozzle on the light emitting element side for preventing the light from directly entering the trap portion.

It is also possible to improve the sensitivity of the sensor by providing a reflecting mirror that faces the light receiving element so that the light receiving element reflects the scattered light of the light emitting element generated in the smoke detecting section.

Further, in the particle detecting sensor according to the present invention, the light emitting element and the light receiving element are arranged so as to be sandwiched by the smoke detecting section and shifted by a predetermined angle from the facing position, and the light emitting element and the light receiving element flow into the smoke detecting section.
In a particle detection sensor that detects particles such as smoke generated in a fire or dust contained in the air, a light shield that prevents direct light from the light emitting element to the light receiving element is provided between the light emitting element and the light receiving element. Since the light-shielding body is provided in the flow path of the sucked air, moisture such as dew is prevented from adhering to the tip of the light-shielding body, and the light from the light-emitting element is incident on the light-receiving element due to the moisture. Is prevented.

[Brief description of drawings]

FIG. 1 is a plan sectional view showing a particle detection sensor according to a first embodiment of the present invention.

FIG. 2 is a plan sectional view showing the flow of air in the sensor of the first embodiment.

FIG. 3 is a front cross-sectional view showing the flow of air in the sensor of the first embodiment.

FIG. 4 is a plan view showing the operation of the first and third light blocking members in the first embodiment.

FIG. 5 is a side cross-sectional view showing a light emitting unit in a particle detection sensor of Example 2.

FIG. 6 is a side sectional view showing a light emitting portion in a modification of the second embodiment.

7 is an enlarged cross-sectional view showing the main parts of FIG.

FIG. 8 is a side sectional view showing a light emitting portion in a particle detection sensor of Example 3;

FIG. 9 is a side sectional view showing a light emitting portion in a modification of the third embodiment.

FIG. 10 is a side sectional view showing a light receiving portion in a particle detection sensor of Example 4.

FIG. 11 is a side sectional view showing a light receiving portion in a modification of the fourth embodiment.

FIG. 12 is a plan sectional view showing a particle detection sensor according to a fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Suction port 2 Suction side air chamber 3 Suction side nozzle 3a Third light shielding member 4 Exhaust side nozzle 5 Exhaust side air chamber 6 Exhaust port 7,17,37 Light emitting part 7a, 17a, 27a, 37a, 47a Light emitting element 8, 18, 28 Light receiving part 8a, 18a, 28a Light receiving element 9 First optical trap part 10 Second optical trap part 20 Reflecting mirror

Claims (9)

[Claims] 1. A light emitting element and a light receiving element are arranged so as to be sandwiched by a smoke detecting section, with a predetermined angle offset from the facing position, and smoke, which is generated at the time of a fire, or dust contained in the air, which has flowed into the smoke detecting section. In a fine particle detection sensor for detecting fine particles, a slit-shaped suction side nozzle arranged so as to face the smoke detection section, and a slit-shaped exhaust side arranged so as to face the smoke detection section facing the suction side nozzle. A fine particle detection sensor comprising a nozzle, and forming a smoke flow path having a slit-shaped cross section from the suction side nozzle to the exhaust side nozzle through a smoke detector. 2. The particle detection sensor according to claim 1, wherein a suction side air chamber and an exhaust side air chamber are connected to the suction side nozzle and the exhaust side nozzle, respectively. 3. The particle detection sensor according to claim 1, wherein the light emitting element includes a plurality of LEDs. 4. A first optical trap portion which is installed so as to face the light emitting element and which prevents light from the light emitting element that has passed through the smoke detecting portion from being reflected and returning to the smoke detecting portion. 4. A second light trap portion, which is installed so as to face the light receiving element, and which prevents the light reflected in the smoke detecting portion from directly entering the light receiving element. The particle detection sensor according to any one of 1. 5. The outer wall surface of the suction side nozzle is used as a first light shielding member for preventing direct incidence of light from the light emitting element to the light receiving element. The fine particle detection sensor described in 1. 6. The outer wall surface of the exhaust side nozzle is used as a second light blocking member for preventing light leaking from the first optical trap portion from directly entering the second optical trap portion. The particle detection sensor according to claim 4. 7. A third light shielding member for preventing light from the light emitting element from being reflected by the tip of the suction side nozzle and directly entering the second light trap portion is provided in the suction side nozzle. The particulate matter detection sensor according to any one of claims 4 to 6, wherein the particulate matter detection sensor is provided on an outer wall surface on the light emitting element side. 8. A reflecting mirror is provided opposite to the light receiving element so as to reflect the scattered light of the light emitted from the light emitting element generated in the smoke detecting section and cause the light receiving element to receive the scattered light.
8. The particulate matter detection sensor according to any one of items 1 to 7. 9. The light emitting element and the light receiving element are arranged so as to be sandwiched between the smoke detecting section and displaced from each other by a predetermined angle from the facing position, so that smoke generated during a fire or dust contained in the air which has flowed into the smoke detecting section. In a particle detection sensor that detects particles, a light shield is provided between the light emitting element and the light receiving element to prevent direct light from the light emitting element entering the light receiving element. A particle detection sensor characterized by being arranged.