JP3731338B2 - Light scattering particle detection sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a light scattering particle detection sensor used to detect dust or cigarette smoke or to detect smoke particles in a photoelectric smoke detector or the like.
[0002]
[Prior art]
This type of light-scattering particle detection sensor includes a light projecting element and a light receiving element that are arranged in an optical chamber so that their optical axes cross each other, and the light projecting area of the light projecting element and the light receiving area of the light receiving element are separated from each other. Particles are detected by receiving, with a light receiving element, scattered light of light from a light projecting element due to particles such as smoke and dust in a detection area that is a polymerization area. The case forming the optical chamber has a double structure or a labyrinth structure for the inflow portion of smoke particles or the like in order to have a structure in which particles such as smoke and dust are easy to flow in and external light is difficult to enter.
[0003]
In this type of conventional light scattering type particle detection sensor, light from the light projecting element is reflected by the inner wall of the optical chamber, the light becomes stray light and reaches the light receiving element, and the optical S / N ratio deteriorates. Has the problem.
[0004]
Therefore, there is a light scattering type particle detection sensor improved in this point as shown in FIG. In this light scattering type particle detection sensor, a light shielding wall 11 is provided in the optical chamber 2 and is surrounded by the light shielding wall 11 and the inner wall of the optical chamber 2 before the light from the light projecting element 4 enters the light receiving element 5. It has a structure that is reflected multiple times in the region. That is, in this light scattering type particle detection sensor, the attenuation of light due to reflection is utilized, and the power of stray light is reduced by increasing the number of reflections. A light shielding unit 10 is provided between the light projecting element 4 and the light receiving element 5 to prevent the light from the light projecting element 4 from entering the light receiving element 5 directly.
[0005]
Further, in the light scattering type particle detection sensor shown in FIG. 5, the light projecting side light trap B configured by making the inner wall of the optical chamber 2 an acute angle on the facing surface of the light projecting element 4 and the surface facing the light receiving element 5. A light receiving side optical trap A having the same configuration is provided. As a result, the light emitted from the light projecting element 4 and guided to the light projecting side light trap B travels back while being reflected on the inner wall, so that the power of stray light can be lowered and temporarily The guided light is prevented from returning to the light projecting element 4 side. Similarly, the light receiving side optical trap A has a structure in which the guided stray light hits the inner wall several times and attenuates and does not return to the light receiving element 5 side.
[0006]
As described above, in the light scattering type particle detection sensor shown in FIGS. 4 and 5, the light emitted from the light projecting element 4 is reflected by the inner wall of the optical chamber 2 and is incident on the light receiving element 5, and the measurement accuracy is improved. In order to prevent deterioration, the stray light ratio (stray light power / projection power) with respect to the projection power becomes weak by suppressing the generation of stray light, and attempts to accurately measure the concentration of particles such as smoke and dust To do.
[0007]
[Problems to be solved by the invention]
However, the light scattering type particle detection sensor having the above-described configuration has a problem that the size of the case itself becomes large in order to suppress the generation of stray light. For example, in the light scattering particle detection sensor shown in FIG. 4, it is necessary to enlarge a region surrounded by the light shielding wall 11 and the inner wall of the optical chamber 2 in order to reflect and attenuate stray light many times. Also in the light scattering type particle detection sensor shown in FIG. 5, in order to sufficiently attenuate the stray light power, the light traps A and B need to be long and large.
[0008]
The present invention has been made in view of the above-mentioned problems, and the object of the present invention is to provide a light-scattering particle that can be further reduced in size without reducing the ability to attenuate stray light. It is to provide a detection sensor.
[0009]
[Means for Solving the Problems]
The invention according to claim 1 is provided with a light projecting element and a light receiving element arranged in the optical chamber so that the optical axes intersect with each other, and the light projecting area of the light projecting element and the light receiving area of the light receiving element are overlapped. In the light scattering type particle detection sensor that detects particles by receiving light scattered from the light projecting element due to particles such as smoke and dust in the detection area, an optical chamber is formed by a hollow rectangular case A light projecting element and a light receiving element are disposed at adjacent corners of the case, and a light trap is provided at each position facing both the light projecting element and the light receiving element, and the light trap facing the light projecting element is opened. its tip as one proceeds from the so as to wrap around the inside of the casing, arranged to face the folded back light receiving element by the folded portion, the tip as a light trap opposed to the light receiving element passes from opening Ke So as to wrap around the inside of the scan, is folded by the folded portion arranged to face the light emitting element, the folded portion, a corner portion opposite to the light emitting element in the case, and the corner portion opposite to the light receiving element Each of the light-emitting elements and the light-receiving element are arranged so as to be positioned, and the wall surfaces intersecting with the optical axis of the light projecting element and the optical axis of the light receiving element are each formed by a curved surface .
[0010]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, a light scattering type particle detection sensor according to an embodiment of the present invention will be described in detail with reference to FIGS. FIG. 1 is a longitudinal sectional view of a light scattering type particle detection sensor according to an embodiment of the present invention. FIG. 2 is an exploded perspective view of the light scattering particle detection sensor according to the embodiment of the present invention. FIG. 3 is a longitudinal sectional view showing the state of light traveling in the light scattering particle detection sensor.
[0011]
In the light scattering type particle detection sensor of the present embodiment, an optical chamber 2 is formed by a hollow rectangular case 1. For the case 1, a black ABS resin or the like is used in consideration of the light reflectivity and the moldability. Even if aluminum or the like subjected to black alumite treatment is used, the reflectance can be lowered, which is effective.
[0012]
The light projecting element 4 and the light projecting lens 17 are provided at the upper left corner of the case 1 and arranged so that the optical axis of the light projecting beam from the light projecting element 4 is emitted toward the lower right corner at the diagonal position. The range through which this projection beam passes is defined as a projection area. Here, as the light projecting element 4, an LED, a semiconductor laser, a solid-state laser, or the like is used. Although the light projecting lens 17 is not always necessary, the light scattering type particle detection sensor according to the present embodiment is used for condensing the light emitted from the light projecting element 4 and concentrating it on the detection region (a).
[0013]
The light receiving element 5 and the light receiving lens 7 are provided in the upper right corner of the case 1 and are arranged so that the optical axis of the region (light receiving region) seen from the light receiving element 5 through the light receiving lens 7 is directed to the lower left corner in the diagonal position. . As the light receiving element 5, a photodiode, a phototransistor, or the like is used. Although the light receiving lens 7 is not always necessary, the light scattering type particle detection sensor of the present embodiment is used to increase the light receiving efficiency.
[0014]
The light-projecting aperture 6 controls the size of the light projecting area of the light projecting element 4 and is used to remove light spreading in the light projecting direction that causes stray light. The aperture 9 on the light receiving side is used not only to control the size of the light receiving area of the light receiving element 5 but also to remove stray light reflected inside the cylinder in which the light receiving element 5 is housed.
[0015]
In the case 1 described above, the printed circuit board 20 that constitutes a processing circuit that appropriately performs signal processing according to the output of the light receiving element 5 on the outer surface of the surface that becomes one side wall of the optical chamber 2 in the shape of a rectangular box with one side opened. The base 1a is mounted, and the cover 1b is attached to the opening of the base 1a.
[0016]
The detection area A is an area where the light projecting area and the light receiving area overlap. Tobacco smoke, dust, and other particles flow into the detection region A from the inlet 3 provided in accordance with the detection region A. The inflow port 3 is provided for the purpose of allowing particles such as smoke and dust to flow into the optical chamber 2, so it does not need to be directly below the detection area A and may be provided at another position. Good.
[0017]
The light emitted from the light projecting element 4 enters the detection area A through the light projection lens 17, the light hitting the particles existing in the detection area A is scattered, and a part of the scattered light enters the light receiving element 5. Since the amount of scattered light increases as the number of particles entering the detection region A from the inflow port 3 increases, the amount of light received by the light receiving element 5 also increases. Therefore, the number of particles (smoke density) can be measured by measuring the amount of received light.
[0018]
In the light scattering particle detection sensor of the present embodiment, for the purpose of removing stray light, the side opposite to the light projecting element 4 on the optical axis of the light projecting beam emitted from the light projecting element 4 as viewed from the detection region A. An optical trap B is provided. Further, an optical trap A is provided on the opposite side of the light receiving element 5 from the detection region A on the optical axis of the light receiving beam incident on the light receiving element 5. The optical trap B has an opening on the optical axis, and the tip of the optical trap B is folded back toward the light receiving element 5 so as to go around the inside of the case 1. Similarly, the optical trap A has an opening on the optical axis, the tip of the optical trap A is folded back projecting element 4 side in such a way as to wrap around the inside of the case 1.
[0019]
When the folding is not performed or when the folding is performed on the side far from the light projecting element 4 and the light receiving element 5, the case 1 becomes very large to store the optical traps A and B. However, as in the present embodiment, the tips of the optical traps A and B are folded back toward the light projecting element 4 and the light receiving element 5 so that the length and size of the optical traps A and B are not changed. Thus, the optical trap B can be stored. This makes it possible to configure a small light scattering particle detection sensor without reducing the ability to attenuate stray light.
[0020]
In the light scattering type particle detection sensor of the present embodiment, the light is projected in a cylindrical shape on the optical axis of the light projection beam emitted from the light projecting element 4 on the side opposite to the light projecting element 4 as viewed from the detection area A. A portion (hereinafter referred to as a first light trap B1 on the light projecting side) having an opening for capturing the light beam and gradually decreasing in diameter is provided, and the tip is folded back to the light receiving element 5 side ( Hereinafter, the folded tip is referred to as a light projecting side second optical trap B2. The size of the opening of the first light trap B1 on the light projecting side is sufficiently large so that all the light emitted from the light projecting element 4 enters the first light trap B1 on the light projecting side. Further, the light axis of the light projecting element 4 and the first light trap on the light projecting side are arranged so that the light entering the first light trap B1 on the light projecting side is reflected and guided to the second light trap B2 on the light projecting side. The wall surface intersecting with B1 is a curved surface. Further, on the optical axis of the light receiving region incident on the light receiving element 5, an optical trap A having the same shape as that arranged on the opposite side of the light projecting element 4 is provided on the side opposite to the light receiving element 5 when viewed from the detection region A. ing.
[0021]
Note that the shapes of the optical traps A and B described above are merely examples, and the first optical traps A1, B1, and second can be used as long as the case 1 has a shape that reduces the size of the case 1 and attenuates incident light. The shapes of the optical traps A2 and B2 and the folded portion are not limited to those described above.
[0022]
In the conventional light scattering type particle detection sensor, since it is necessary to enlarge the optical traps A and B in order to suppress stray light, it is a problem that miniaturization and reduction of stray light cannot be compatible. However, according to the light scattering type particle detection sensor of the present embodiment, a part or all of the light traps A and B are placed in a space (dead space) in the optical chamber 2 where nothing has been conventionally installed. Therefore, the space utilization efficiency in the optical chamber 2 can be improved, and the size can be reduced without reducing the effect of attenuating stray light.
[0023]
In this type of light scattering type particle detection sensor, dust tends to accumulate on the inner wall of the optical chamber 2, and stray light caused by reflection on the dust becomes a problem. However, in the present embodiment, the tip portions of the optical traps A and B where dust is most likely to accumulate are folded back as the second optical traps A2 and B2. It has the effect that it is difficult to collect and stray light generated due to dust can be reduced. Even if dust is generated on the light projecting axes in the optical traps A and B, the specular reflection component having the strongest scattered light power is reflected in the back of the optical traps A and B. Can be suppressed.
[0024]
【The invention's effect】
As described above, the invention according to claim 1 includes the light projecting element and the light receiving element arranged in the optical chamber so that the optical axes intersect with each other, and the light projecting area and the light receiving element of the light projecting element. in the light scattering particle sensor for detecting particles by receiving scattered light from the light emitting element by the light receiving element by particles, such as smoke and dust in the detection region is a region where the light receiving region is polymerized in a hollow rectangular the optical chamber formed by the mold of the case, the light projecting element and a light receiving element disposed at a corner portion adjacent the casing, a light trap is provided in a position respectively to both facing the light projecting element and a light receiving element, projecting its tip casing as the tip as a light trap opposed to the light element advances from opening arranged as folded in such a way as to wrap around the inside of the case toward the light receiving element, light trap opposed to the light receiving element passes from the opening It is folded so as to wrap around the inner disposed to face the light emitting element, since the arrangement of the tips of both optical traps in the dead space of the optical chamber, it is possible to improve the utilization efficiency of the space, attenuating stray light There is an effect that it is possible to provide a light scattering type particle detection sensor capable of further downsizing without lowering the capability.
[Brief description of the drawings]
FIG. 1 is a longitudinal sectional view of a light scattering particle detection sensor according to an embodiment of the present invention.
FIG. 2 is an exploded perspective view of a light scattering particle detection sensor according to an embodiment of the present invention.
FIG. 3 is a longitudinal sectional view showing the state of light traveling in the light scattering particle detection sensor.
FIG. 4 is a longitudinal sectional view of a conventional light scattering type particle detection sensor.
FIG. 5 is a longitudinal sectional view of another conventional light scattering type particle detection sensor.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Case 2 Optical chamber 4 Light emitting element 5 Light receiving element A Light receiving side light trap B Light emitting side light trap A1 Light receiving side first light trap A2 Light receiving side second light trap B1 Light emitting side first light trap B2 Optical side second optical trap light detection area

Claims (1)

Smoke and dust in the detection area, which is a region where the light projecting area of the light projecting element and the light receiving area of the light receiving element are superposed, each having a light projecting element and a light receiving element arranged in the optical chamber so that the optical axes intersect each other In a light scattering type particle detection sensor that detects particles by receiving scattered light from a light projecting element due to particles such as particles, an optical chamber is formed by a hollow rectangular case, and adjacent corner portions of the case A light projecting element and a light receiving element are provided on each of the light traps, and a light trap is provided at each position facing both the light projecting element and the light receiving element. so as to wrap around the inner, arranged to face the folded back light receiving element by the folded portion, the tip as a light trap opposed to the light receiving element passes from the opening flows around the inside of the case A manner, folded by the folded portion arranged to face the light emitting element, the folded portion, a corner portion opposite to the light emitting element in the case, and to be located respectively in the corner facing the light receiving element distribution And a light scattering particle detection sensor characterized in that the optical axis of the light projecting element and the wall surface intersecting with the optical axis of the light receiving element are each curved .

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