JPH08261930A - Fine grain detecting sensor - Google Patents

Abstract

PURPOSE: To provide a fine grain detecting sensor capable of being miniaturized and surely detecting fine grains of a large quantity of air at a high S/N ratio. CONSTITUTION: The light emitted from a light emitting element 1 is converted into parallel light 3 by a lens 2, and a light receiving element 4 detects the scattered light from the fine grains existing in the fan-shaped field pattern 6 expanded along the optical path of the parallel light 3. The parallel light 3 passing through the field pattern 6 enters a light trap section 7 having a sealed box structure from an opening section 7a, and it is attenuated here. Since the parallel light 3 and the light trap section 7 are used, the stray light can be processed in a small space. Since the scattered light of the parallel light 3 caused by fine grains is detected by the fan-shaped field pattern 6, fine grains in a large quantity of air can be detected at a high S/N ratio.

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 Generally, a particle detection sensor such as a highly sensitive smoke sensor or dust monitor emits a light beam from a light source to a detection area and detects scattered light from the particles existing in the detection area. It is detecting. As the light source, an LED (light emitting diode), an LD (semiconductor laser), a xenon lamp, or the like is used.

A light beam emitted from a light source is spread in a conical shape or spot-focused to enter a detection area. When a light beam spread in a conical shape is used, the detection area can be set wide, but when light is widely radiated, reflection occurs on the inner wall surface of the detection area, etc. Also, light called stray light that is not scattered light is easily observed at the light receiving portion. Therefore, in order to construct an optical system with a high S / N ratio, a large space for processing stray light is required, and the particle detection sensor becomes large. On the other hand, if spot focusing is performed, high S / N
Although a ratio optical system can be obtained, it is not suitable for detecting fine particles in a large amount of air because the detection area becomes extremely small.

Further, since the scattered light from the fine particles becomes extremely weak, in order to reliably detect the fine particles,
It is desirable to use a light source with a large amount of light. However,
A large amount of light source generally has a large amount of heat generation and a large temperature dependency, and there is a possibility that desired light emission characteristics may not be obtained when the temperature rises.

[0005]

As described above, in the conventional fine particle detection sensor, when the light beam which is spread in a conical shape is used, a high S / N ratio cannot be obtained unless the entire sensor is enlarged. On the other hand, when a light beam focused on a spot is used, it is difficult to detect a large amount of air particles. Further, in the conventional particle detection sensor, there is a problem in that when the light source is driven, the desired light emission characteristic cannot be obtained due to the temperature rise, and thus the particles cannot be reliably detected. The present invention has been made in order to solve such a problem, and an object thereof is to provide a particle detection sensor which is small in size and can reliably detect a large amount of air particles with a high S / N ratio. And

[0006]

A fine particle detection sensor according to a first aspect of the present invention is a photoelectric type fine particle for detecting fine particles such as smoke generated during a fire or fine particles such as dust contained in the air from the sucked air. A detection sensor, a light emitting means,
An optical element for converting the light emitted from the light emitting means into parallel light, and a parallel light by fine particles having a fan-shaped field pattern extending along the optical path of the parallel light converted by the optical element and existing in this field pattern. A light-receiving means for detecting scattered light of, and an opening provided in front of the light-emitting means, into which the parallel light is incident, and having a reflection surface inside which is oblique to the parallel light and which is directly irradiated with the parallel light. An optical trap portion having a box structure is housed in a casing, and an air inlet into which sucked air flows in and an air outlet from which the sucked air flows out are provided in the casing.

According to a second aspect of the present invention, there is provided the particle detection sensor according to the first aspect, wherein the light emitting means is arranged in an air flow path from the air inlet to the air outlet.
The particle detection sensor according to claim 3 is the sensor according to claim 1 or 2, wherein one of the air inlet and the air outlet is in the vicinity of the light emitting means, and the other is on an extension of the optical path of the light emitted from the light emitting means. They are arranged respectively. The particle detection sensor according to claim 4 is the sensor according to claim 1 or 2, wherein the air inlet and the air outlet each have a slit shape, and the air formed between the air inlet and the air outlet is formed. The flow path intersects the optical path of the light emitted from the light emitting means.

[0008]

In the fine particle detection sensor according to claim 1,
The light emitted from the light emitting means is converted into parallel light by the optical element, and the light receiving means detects the scattered light from the fine particles existing in the fan-shaped field pattern spreading along the optical path of the parallel light, and the light trap section receives the light. The parallel light that has passed through the field pattern of the means is captured, and this parallel light is prevented from entering the light receiving means. Since the scattered light of the parallel light by the fine particles is detected by the light receiving means having the fan-shaped field pattern and the stray light is reduced by the light trap portion, a large amount of fine particles can be detected with a high S / N ratio.

According to a second aspect of the present invention, in the fine particle detection sensor according to the first aspect, since the light emitting means is arranged in the air flow path, the light emitting means can be cooled by the air flow.

According to a third aspect of the present invention, there is provided the particle detection sensor according to the first or second aspect, wherein one of the air inlet and the air outlet is in the vicinity of the light emitting means, and the other is the optical path of the light emitted from the light emitting means. It is arranged on each extension line. As a result, the sucked air is caused to flow along the optical path of the light from the light emitting means, and the fine particles are reliably detected.
Further, in the particle detection sensor according to claim 4, in the sensor according to claim 1 or 2, the slit-shaped air inlet and the slit-shaped air outlet have an air flow path formed therebetween. It is arranged so as to intersect with the optical path of light from the light emitting element. Thereby, the sucked air surely passes through the optical path of the light from the light emitting element, and the fine particles are detected.

[0011]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Example 1. 1 and 2 show Embodiment 1 of the present invention.
The sectional view and front view of the particle detection sensor according to the present invention are shown. An optical chamber 10a is defined inside the casing 10,
An inlet port 8 is formed at one end of the casing 10 for taking in the air in the room, which is the target of particle detection. A light emitting element 1 is provided inside the inflow port 8 as a light emitting means, and a lens 2 is arranged in front of the light emitting element 1. As the light emitting element 1, LD (semiconductor laser), LE
D (light emitting diode) or the like can be used. The lens 2 acts as an optical element for converting the light emitted from the light emitting element 1 into the parallel light 3 and can be formed of a single lens such as an aspherical lens, but a highly accurate parallel light is obtained by using a combination lens. 3 can also be formed. Further, by inserting an optical diaphragm (pinhole) on the front surface of the lens, light with less flare can be obtained. The light emitting element 1
The lens 2 and the lens 2 are provided in, for example, a bottomed cylindrical holder 11 having an opening formed on the front surface through which the parallel light 3 passes.
The holder 11 is supported in the inflow port 8 by a plurality of columns (not shown).

The parallel light 3 so that the parallel light 3 does not directly enter
A light-receiving element 4 serving as a light-receiving means is arranged at a position deviated from the optical path of. The light receiving element 4 is oriented in a direction having a predetermined angle with respect to the optical path of the parallel light 3, and a plurality of optical diaphragms 5 are arranged in front of the light receiving element 4. Each optical diaphragm 5 has an elongated rectangular opening 5 as shown in FIG.
a, and the lengthwise direction of the opening 5a is arranged so as to be parallel to the paper surface in FIG. Further, the optical diaphragm 5 located farther from the light receiving element 4 has a longer opening 5a, and the optical diaphragm 5 closer to the light receiving element 4 has a shorter opening 5a. The width of the opening 5a is
It is set to a constant value in any of the optical diaphragms 5. As a result, the light receiving element 4 has a fan-shaped field pattern (field of view) 6 having the width of the opening 5a of the optical diaphragm 5 that spreads along the optical path of the parallel light 3 unlike the conventional conical field pattern. It will be. Thus, the narrower the width of the opening 5a, the more the stray light is prevented from entering the light receiving element 4, and the width is appropriately set according to the size of the parallel light emitted from the light emitting means 1. Light receiving element 4
The plurality of optical diaphragms 5 form the light receiving means of the present invention.

An optical trap portion 7 is formed on the other end side of the casing 10 so as to face the light emitting element 1 and the lens 2. The optical trap portion 7 has a substantially closed box structure,
It has an opening 7a located on the optical path of the parallel light 3.
The size of the opening 7a is set to be slightly larger than the cross-sectional shape of the parallel light 3 and is set so that the parallel light 3 does not hit the peripheral edge of the opening 7a. Inside the optical trap section 7,
First to fourth reflecting surfaces 7b to 7e each having a low reflectance are formed. The first reflection surface 7b is positioned obliquely with respect to the optical path of the parallel light 3 so that the parallel light 3 incident from the opening 7a is reflected toward the second reflection surface 7c. The third reflecting surface 7d is arranged in parallel with each other, and the fourth reflecting surface 7e connects the end portions of the second and third reflecting surfaces 7c and 7d to each other so as to block the optical path. Further, a plurality of fins 7f are provided between the opening 7a and the first reflecting surface 7b and in the peripheral portion of the optical path of the parallel light 3 incident from the opening 7a.
Is provided.

A flow path for air taken in from the inflow port 8 is formed in the outer peripheral portion of the light emitting element 1 and the lens 2 arranged in the inflow port 8. On the other hand, an air outlet 7g is formed in the wall portion between the fins 7f adjacent to each other in the optical trap portion 7, and the outlet 7g is further provided in the other end of the casing 10.
Is formed with an outlet 9. Therefore, when the air in the room is sucked into the inflow port 8 by a suction device (not shown) or the like, the air flows through the flow path formed in the outer peripheral portion of the light emitting element 1 and the lens 2 as shown by the broken line in FIG. After flowing through the casing 10 into the casing 10, it enters the optical trap portion 7 through the opening 7a, and then flows out of the particle detection sensor through the outlet 7g and the outlet 9.

Next, the operation of the particle detection sensor according to the first embodiment will be described. First, a predetermined power source is supplied to the light emitting element 1 from a power source device (not shown), for example, to periodically emit light. The light emitted from the light emitting element 1 becomes parallel light 3 by passing through the lens 2, and goes straight toward the opening 7 a of the light trap portion 7. At this time, since the parallel light 3 is formed by the lens 2, the reflected light due to the inner wall surface of the casing 10 causing the stray light hardly enters the light receiving element 4. The parallel light 3 that has passed through the field pattern 6 of the light receiving element 4 enters the optical trap portion 7 through the opening 7a.

As shown in FIG. 4, the collimated light 3 which has passed through the opening 7a reaches the first reflecting surface 7b of the light trap portion 7, and all of the light is second light due to the angle of this surface 7b. After being reflected by the reflecting surface 7c, the second reflecting surface 7c to the third reflecting surface 7c
To the reflection surface 7d. The distance between the end of the third reflection surface 7d and the first reflection surface 7b can be set to about the size of the opening 7a if the parallel light 3 is a perfect parallel light. Since there is a possibility that the light may be slightly spread or narrowed down in manufacturing, the distance is set so as to allow the light to pass according to the manufacturing variation, and at the same time, all the light reflected by the second reflecting surface 7c is the third reflecting surface. The spacing must be such that 7d can be reached. The light reflected by the third reflection surface 7d then repeats reflection between the second reflection surface 7c and the third reflection surface 7d that are in a parallel positional relationship, and reaches the fourth reflection surface 7e. Since each of the reflecting surfaces 7b to 7e is formed to have a low reflectance, the light quantity of the reflected light is gradually attenuated as the number of reflections increases.

The light reflected by the fourth reflecting surface 7e is again converted into the second light.
The reflective surface 7c and the third reflective surface 7d repeatedly return and return. However, since the main light beam does not reflect on the surface orthogonal to it in the light trap portion 7, it does not go back to the light emitting point by going backward in the same optical path.
The second reflecting surface 7c and the third reflecting surface 7d are preferably parallel to each other because the number of reflections between them is reduced and the amount of light attenuation is reduced unless they are in a parallel positional relationship.

In this way, the light quantity is attenuated by being reflected by each reflecting surface in the light trap portion 7, but there is also light that repeats reflection and returns to the opening portion 7a. Most of the light is reflected by the plurality of fins 7f, returns to the inside of the light trap portion 7, and is attenuated. Further, even if there is light emitted from the optical trap portion 7 through the opening 7a without being blocked by the fins 7f, the direction thereof is limited to the directions of the light emitting element 1 and the lens 2 by the action of the plurality of fins 7f. It does not enter the light receiving element 4. Therefore, it is possible to realize an output signal from the light receiving element 4 in which the particles are not present in the casing 10 is very small. The optical trap unit 7
Since the discharge port 7g communicating with the outflow port 9 is provided inside, even if external light enters from the outflow port 9 into the particle detection sensor,
Similar to the attenuation of the parallel light 3 described above, the external light is absorbed by the optical trap unit 7.
It is attenuated inside and outside light does not affect the detection of particulates.

In this state, when air, etc. in the room, which is the object of particle detection, is sucked into the inlet 8 by a suction device (not shown), the air is emitted from the rear of the holder 11 toward the front thereof. After passing through the flow path on the outer peripheral portion of the lens 2, the light flows toward the opening 7 a of the optical trap portion 7. That is, the air flows along the optical path of the parallel light 3. At this time, the scattered light of the parallel light 3 is generated by the fine particles contained in the air flow, and the scattered light is captured by the light receiving element 4, and the detection output is obtained from the light receiving element 4.

As described above, when the collimated light 3 is emitted from the light emitting element 1, by providing the inflow port 8 in the vicinity of the light emitting element 1 and the outflow port 9 in the vicinity of the extension line of the optical path of the collimated light 3, the parallel light 3 is emitted. An air flow path can be formed around the light 3. Therefore, the field pattern 6 which is the detection area
The smoke can be reliably guided to the inside of the casing, and the inner wall of the casing 10 is prevented from being contaminated by the air flow. Further, since the inflow port 8 is provided at the rear of the light emitting element 1, the lens 2 in the holder 11 is not contaminated.

Here, since the light receiving element 4 has the fan-shaped field pattern 6 which spreads along the optical path of the parallel light 3 by the plurality of optical diaphragms 5, it is generated in a wide range along the optical path of the parallel light 3. The scattered light can be effectively detected, and a large received light intensity can be obtained. The reason why the field pattern 6 of the light receiving element 4 can be expanded in a fan shape is that stray light is less due to the use of the parallel light 3. Since fine particles are detected in a wide detection area along the optical path of the parallel light 3, a large amount of air can be detected at the same time.

Since the holder 11 for accommodating the light emitting element 1 and the lens 2 is arranged in the flow path of the sucked air,
The light emitting element 1 is forcibly and automatically cooled by the air flow via the holder 11. Therefore, even if an element such as a semiconductor laser having a large heat generation amount or temperature dependency is used as the light emitting element 1, it can be driven well. Note that if the pillars of the holder 11 are formed in a thin blade shape and a material having high heat dissipation is used, the heat dissipation effect is further enhanced. Moreover, the amount of air to be sucked in, that is, the flow rate can be set by the support.

Embodiment 2 FIG. Instead of the plurality of optical diaphragms 5 used in the first embodiment, a cylindrical lens 15 as shown in FIG. 5 may be arranged in front of the light receiving element 4. By arranging the cylindrical lens 15 so that the cylindrical axis A is perpendicular to the paper surface of FIG. 1, it becomes possible to form the sectoral field pattern 6 as in the first embodiment.
Since only one cylindrical lens 15 is required, the structure is simple. The cylindrical lens 15 may be used together with the optical diaphragm 5 having a rectangular opening as shown in FIG.

Example 3. In Example 1, the air flow was formed from the rear to the front of the cylindrical holder 11 that accommodates the light emitting element 1 and the lens 2, but as shown in FIG.
The flow path 18a can also be formed so that the air sucked into the inflow port 18 flows in a direction perpendicular to the cylindrical light emitting unit 21. A plurality of cooling fins 22 are formed on the outer peripheral portion of the light emitting portion 21 in parallel to the flow of air in the flow path 18a.
Since the light emitting portion 21 is provided so as to penetrate the flow path 18a in the direction perpendicular to the light emitting portion 21, as shown in FIG.
The flow path 18a is formed on both sides of. A light emitting element 1 and a lens 2 are provided in the light emitting section 21.
The drive circuit 23 is connected to.

With such a structure, the air sucked through the inflow port 18 effectively contacts the cooling fins 22 formed in parallel with the air flow, and the light emitting section 21.
Is forcibly and automatically cooled and then introduced into the optical chamber 20a from the vicinity of the tip of the light emitting section 21. Therefore, the cooling efficiency of the light emitting unit 21 and thus the light emitting element 1 is improved, and even if an element having a large heat generation amount or temperature dependency such as a semiconductor laser is used as the light emitting element 1, it can be driven well.

Example 4. In the particulate matter detection sensor of the second embodiment, as shown in FIG. 8A, an air bypass passage 12 is formed in the air introduction portion that takes in air into the sensor from the outside, and the air passage 18a and the bypass passage 12 are formed. A blocking means 13 for restricting the flow of air may be provided between the two. The shut-off means 13 is made of a well-known shape memory substance, and is in an extended state at room temperature as shown in FIG. 8 (a) so as to shut off the space between the inflow port 18 and the bypass passage 12 and to flow through the inflow port 18. When communicating with the passage 18a, when the temperature is higher than a predetermined temperature, the passage 18a is bent as shown in FIG.
8a and the inflow port 18 to the bypass passage 1
Connect to 2.

By providing the shut-off means 13 as described above, the air taken in the inflow port 18 at the normal time is made to flow through the flow path 1.
8a to cool the light emitting part 21, and when a high temperature hot airflow flows into the inflow port 18 due to a fire or the like, the blocking means 13 bends to introduce the hot airflow from the bypass passage 12 into the optical chamber 20a. It becomes possible. Therefore, it is possible to prevent the light emitting section 21 from being heated by the hot air flow and detect smoke or the like by the air introduced from the bypass passage 12.

Example 5. In each of the above-described embodiments, by introducing air into the casings 10 and 20 from the vicinity of the light emitting element 1 and forming the air outlet 7g in the light trap portion 7, the parallel light 3 from the light emitting element 1 is emitted. An air flow as shown by the broken line in the figure was formed along the optical path.
As shown in, the flow path may be formed so that the air flow intersects the optical path of the parallel light 3 in the detection area of the light receiving element 4. A cylindrical introduction path 32 and a cylindrical introduction path 33 are connected to the inflow port 28 and the outflow port 29 of the casing 30, respectively.
Elongated slit-shaped openings 32a and 33 through which air flows at the tip ends of the inlet passage 32 and the outlet passage 33, respectively.
a is formed. The openings 32a and 33a are opposed to each other with the optical path of the parallel light 3 emitted from the light emitting section 31 interposed therebetween, and the optical path and the air flow path are in contact with each other in a substantially linear manner, not in a point. . The sucked air flows from the inflow port 28 to the outflow port 29 along the flow path shown by the broken line in FIG. 8, and in the detection area of the light receiving element 4, flows obliquely to the optical path of the parallel light 3. Become. With such a configuration, the light receiving element 4 can detect scattered light due to fine particles in the air. The slit-shaped openings 32a and 33a are used to make the cross-sectional shape of the air flow slit-shaped because the height of the smoke flow passage is increased in order to prevent pressure loss due to the reduction of the flow passage cross-sectional area. This is to make it larger.

Further, elongated slit-shaped inlets and outlets may be provided at positions where the plane including the optical path of the parallel light from the light emitting element intersects with the casing.
For example, in FIG. 9, the introduction passage 32 is provided parallel to the paper surface, but the introduction passages are provided on the left and right outer walls of the casing 30 so that the flow path of the sucked air is perpendicular to the paper surface. It may be formed. Even in this case, since the sucked air can be guided to parallel light, smoke can be reliably detected. Although the case where the light emitting element is provided near the inflow port is shown, the light emitting element may be provided near the air outflow port, and the air outflow port may be provided on an extension of the optical path of the light emitted from the light emitting element. .

[0030]

As described above, the fine particle detection sensor according to the present invention is a photoelectric type fine particle for detecting fine particles such as smoke generated at the time of fire or dust contained in the air from the sucked air. The detection sensor has a light emitting means, an optical element for converting the light emitted from the light emitting means into parallel light, and a fan-shaped field pattern extending along the optical path of the parallel light converted by the optical element, and Light receiving means for detecting scattered light of parallel light due to fine particles existing in the field pattern, and provided in front of the light emitting means,
An air trap part having a closed box structure having an opening for incident parallel light and having a reflection surface inside which is obliquely positioned with the parallel light and is directly irradiated by the parallel light is housed in the casing, and the sucked air is Since the casing is provided with an inflow air inlet and an air outlet for sucking air out to the outside, it is possible to reduce stray light and detect a large amount of fine particles of air with a high S / N ratio while being compact. It will be possible.

By arranging the light emitting means in the air flow path from the air inlet to the air outlet, even if heat is generated by driving the light emitting means, the light emitting means is cooled by the sucked air flow. Therefore, the reliability of particle detection is improved.

If one of the air inlet and the air outlet is arranged in the vicinity of the light emitting means and the other is arranged on the extension line of the optical path of the light emitted from the light emitting means to form a particle detection sensor, the light emitted from the light emitting means is formed. It is possible to form an air flow along the optical path of, and it is possible to reliably detect the fine particles. Further, if each of the air inlet and the air outlet has a slit shape, and the air passage formed between the air inlet and the air outlet is configured to intersect with the optical path of the light emitted from the light emitting means, The sucked air surely passes through the optical path of the light from the light emitting means, and the fine particles are surely detected.

[Brief description of drawings]

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

2 is a front view showing a particle detection sensor of Example 1. FIG.

3 is a front view showing an optical diaphragm used in Example 1. FIG.

FIG. 4 is an optical path diagram showing the operation of the optical trap portion in the first embodiment.

FIG. 5 is a perspective view showing a cylindrical lens used in the particle detection sensor according to the second embodiment.

FIG. 6 is a side sectional view showing a particle detection sensor according to a third embodiment.

FIG. 7 is a plan sectional view showing a cross section of a light emitting portion of a particle detection sensor of Example 3;

8A and 8B show an air introduction part used in a particle detection sensor according to a fourth embodiment, FIG. 8A is a side sectional view showing a normal state, and FIG. 8B is a side sectional view showing a state when a hot air flow is introduced. It is a figure.

FIG. 9 is a side sectional view showing a particle detection sensor according to a fifth embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Light emitting element 2 Lens 3 Parallel light 4 Light receiving element 7 Optical trap part 7a Opening part 8,18,28 Inlet port 9,29 Outlet port 10,20,30 Casing 11 Holder

Claims (4)

[Claims] 1. A photoelectric type particle detection sensor for detecting, from the sucked air, smoke generated during a fire or particles such as dust contained in the air, comprising: a light emitting means, and a light emitting means emitting light from the light emitting means. An optical element for converting the collimated light into parallel light, and a scattered light of the collimated light by fine particles having a fan-shaped field pattern spreading along the optical path of the parallel light converted by the optical element and present in this field pattern. And a light-receiving means for detecting the light, and a sealed box provided in front of the light-emitting means, having an opening through which the parallel light is incident, and having a reflecting surface positioned obliquely to the parallel light and directly irradiated with the parallel light. The optical trap part of the structure was housed in the casing, and the casing was provided with an air inlet into which the sucked air flows and an air outlet from which the sucked air flows out. Particulate matter detection sensor according to claim. 2. The particle detection sensor according to claim 1, wherein the light emitting means is arranged in an air flow path from the air inlet to the air outlet. 3. One of the air inlet and the air outlet is arranged near the light emitting means, and the other is arranged on an extension line of an optical path of light emitted from the light emitting means. Alternatively, the particle detection sensor described in 2. 4. The air inlet and the air outlet each have a slit shape, and an air flow path formed between the air inlet and the air outlet is an optical path of light emitted from the light emitting means. The fine particle detection sensor according to claim 1 or 2, wherein the fine particle detection sensor intersects with each other.