JP2019082336A - Particulate detection sensor - Google Patents

Abstract

To provide a particulate detection sensor capable of stabilizing an output in a short time.SOLUTION: A particulate detection sensor 100 comprising a light emitting element 110, a condenser lens 120, a light receiving element 130, and a controller 140 irradiates a detection region R with a light beam L output from the light emitting element 110 and detects scattered light L' generated by the light beam L striking a particulate P in the detection region R by using the light receiving element 130. The light emitting element 110 is formed as a multibeam light source having a plurality of light emitting points 110b in a light emitting surface 110a.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a particulate matter detection sensor that detects particulates such as dust in the air and cigarette smoke.

  The particle detection sensor is capable of detecting the presence or absence of particles by irradiating the detection area with the output light (irradiation beam) from the light emitting element and detecting the scattered light generated on the particles in the detection area with the light receiving element. In detail, the density (soiling degree) of fine particles and the type of fine particles can be detected according to the amount (brightness) of scattered light and the detection frequency.

  Many conventional particle detection sensors employ a particle count method for counting the particle diameter and the number of particles captured by the irradiation beam. As a lighting method of a light emitting element (such as an LED) which outputs an irradiation beam, there are a constant light emitting method and a pulse lighting method. From the viewpoint of suppressing the aged deterioration of the light emitting element, a pulse lighting method in which light emission of the light emitting element is repeated for a short time is preferable. For example, Patent Documents 1 and 2 disclose a particle detection sensor using such a pulse lighting method.

JP, 2016-224034, A JP 2004-294082 A

  In the conventional particle detection sensor, since all the light emitting elements are single light sources (single beam), the area which can actually be detected is narrow, and the particles are not detected unless they pass through the area, so the output is stabilized in a short time I could not do it.

  Furthermore, when the lighting method of the light emitting element is always the light emitting method, the output can be stabilized in a short time as compared with the other methods because particulates can be detected whenever the particles pass through the area, but the power consumption increases. There is a problem that aging deterioration of the light emitting element is promoted. In addition, in the pulse lighting method, there is a problem in that particulates passing through the area can not be detected if the light emission timing does not match.

  That is, in the case of using a pulse lighting method for the light emitting element, a period in which the scattered light can be detected by the light receiving element (that is, the particulates are detected) corresponds to the light emitting period of the light emitting element. Further, in the particle count method, when the number of particles is counted with detection data corresponding to one pulse light emission, a large variation occurs in the detection result. Therefore, in order to stabilize the output of the particle detection sensor (to ensure detection accuracy), detection data corresponding to a large number of pulse light emissions are required. Therefore, in the conventional particulate matter detection sensor, there is a problem that a relatively long time is required to cause the light source to perform pulse emission many times before the output is stabilized.

  The present invention is made in view of the above-mentioned subject, and an object of the present invention is to provide a particulate matter detection sensor which can stabilize an output in a short time.

  In order to solve the above-mentioned problems, the present invention is a particulate detection sensor which irradiates output light from a light emitting element to a detection area, and detects scattered light generated on fine particles in the detection area by a light receiving element, The light emitting element is characterized in that it is a multi-beam light source having a plurality of light emitting points on the light emitting surface.

  According to the above configuration, by using the light emitting element as a multi-beam light source, a plurality of output lights can be spread around the detection region, the count frequency of particle detection increases, thereby increasing the detection probability. The output can be stabilized in a short time as compared with the single beam configuration).

  Further, in the particle detection sensor, the output light from each light emitting point of the light emitting element may be pulse light.

  According to the above configuration, the effects of power saving and long life of the light emitting element can be obtained as compared with the case where the light emitting element is always lit. In addition, in the conventional pulse lighting drive, there was a problem that it takes time to stabilize the output, but since the present invention can obtain the effect of stabilizing the output in a short time, the application to the pulse lighting drive is effective It is.

  In the particle detection sensor, the light emitting element may be a VCSEL.

  According to the above configuration, the output light from the light emitting element can be narrowed to a small beam spot, and the frequency of the sufficiently narrowed output light may hit the fine particles. Therefore, the detection signal output from the light receiving element is less likely to fluctuate depending on the position of the particle with respect to the beam spot, and the output of the particle detection sensor becomes more stable.

  Further, the particulate matter detection sensor may be configured to have an optical system for condensing the output light emitted from the light emitting element toward the detection area.

  Furthermore, in the particle detection sensor, the optical system may be configured to include a condensing lens that condenses the output light, and an adjustment lens that adjusts the output light transmitted through the condensing lens to be longer and narrower. it can.

  According to the above configuration, by configuring the optical system with the condensing lens and the adjusting lens, it is possible to narrow the output light from the light emitting element, that is, narrow the output light crossing the detection area. Even if it does not, it becomes possible to detect particles, the detection probability is further increased, and the output can be stabilized in a short time.

  Further, in the particle detection sensor, the plurality of light emitting points in the light emitting element may be arranged concentrically.

  According to the above configuration, the arrangement intervals of the plurality of light emitting points become more uniform, and the probability of passing through the beam spot becomes difficult to change due to the route through which the particles pass in the detection area. Thereby, the output of the particle detection sensor is more stable.

  The particle detection sensor of the present invention has an effect that the output can be stabilized in a short time as compared with the conventional configuration (single beam configuration) by using the light emitting element as a multi-beam light source.

FIG. 1 is a schematic view showing a basic configuration of a particulate matter detection sensor according to Embodiment 1. 5 is a timing chart showing an example of light emission timing of a light emitting element in the particulate matter detection sensor of the first embodiment. It is a wave form diagram which shows an example of the detection signal in the particulate matter detection sensor which made the light emitting element the LED light source. FIG. 8 is a schematic view showing a basic configuration of a particulate matter detection sensor according to Embodiment 2. (A)-(c) is a top view which shows the example of arrangement | positioning of the light emission point in the light-projection surface of a light emitting element.

First Embodiment
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view showing a basic configuration of a particle detection sensor 100 according to the first embodiment. The particle detection sensor 100 is configured to include a light emitting element 110, a condensing lens 120, a light receiving element 130, and a control unit 140.

  The light emitting element 110 is a multi-beam light source having a plurality of light emitting points 110 b on the light emitting surface 110 a. Preferably, a vertical cavity surface emitting laser (VCSEL) is used as the light emitting element 110.

  The condensing lens 120 is a lens for condensing the light beam (output light) L emitted from each light emitting point 110 b of the light emitting element 110 toward the detection region R. In the light emitting element 110, the detection region R is a region near the focusing point of the light beam L. Incidentally, the particle detection sensor 100 has a particle passage hole (not shown) in a part of the housing, and by taking in the particles in the passage hole, high precision detection can be performed in a short time. It is configured. That is, in the particle detection sensor 100, a detection region R exists inside the passage hole. It is needless to say that well-known techniques and well-known techniques may be applied as a method for guiding the fine particles to the passage holes. For example, any of an air blowing / suction system and an air flow generation system based on a temperature difference may be adopted. In addition, it is needless to say that the use of the air blowing / suction method or the air flow generation method is not particularly required in the installation environment of the particle detection sensor in which the particles are naturally led to the passage holes.

  The light beam L condensed by the condensing lens 120 is scattered (specular reflection or irregular reflection) when it is irradiated to the fine particles P present in the detection region R, and thereby the scattered light L 'is generated. The light receiving element 130 receives and detects the scattered light L '. That is, the light receiving element 130 outputs an electrical signal according to the light amount of the received scattered light L '.

  The control unit 140 outputs a drive signal for driving the light emitting element 110 to emit light, and detects the density (soiling degree) of the particles, the type of the particles, and the like based on the electric signal output from the light receiving element 130.

  In the particle detection sensor 100 according to the first embodiment, the plurality of collected light beams L can be spread around the detection region R by causing the plurality of light emitting points 110 b of the light emitting element 110 to emit light simultaneously. That is, by simultaneously generating a plurality of light beams L during the light emission period of the light emitting element 110, the count frequency of particle detection increases, thereby increasing the detection probability and stabilizing the output of the particle detection sensor 100 in a short time. Can. For example, when the number of light emitting points 110b of the light emitting element 110 is m, the time required for stable output can be reduced to 1 / m as compared with the conventional configuration (single beam configuration).

  Further, the light emission timing of the plurality of light emitting points 110 b in the light emitting element 110 is not limited to simultaneous light emission as described above, and it is also possible to cause the plurality of light emitting points 110 b to emit light with a phase shift.

  FIG. 2 is a timing chart showing an example in which the phase of the light emission timing of the light emitting element 110 in the particle detection sensor 100 is shifted. Here, it is assumed that the light emitting element 110 has m light emitting points 110 b for pulse light emission, and the pulse light emitting interval of each light emitting point 110 b is the shortest time T.

  As shown in FIG. 2, the light emission timings of the light beams L1 to Lm emitted from each of the m light emitting points 110b are shifted by T / m. That is, although the number of light emitting pulses during time T is one in a single beam emitted from one light emitting point 110b, the number of light emitting pulses during time T is m in a multi beam emitted from the entire light emitting element 110. It will be times.

  As described above, when the light emitting element 110 uses the pulse lighting method, the period in which the light receiving element 130 can detect the scattered light L ′ corresponds to the light emitting period of the light emitting element 110. Further, in the particle counting method, in order to stabilize the output of the particle detection sensor 100 (to ensure detection accuracy), detection data corresponding to a large number of pulse light emissions are required.

  Here, if it is necessary to use n times of pulsed light emission in order to stabilize the output in the particle detection sensor 100, in the conventional particle detection sensor using a single beam, it takes n × T time to stabilize the output. Is required. On the other hand, in the particle detection sensor 100 according to the first embodiment, since the number of light emission pulses during time T is m, the time required to stabilize the output is (n × T) / m. As compared with the conventional configuration (single beam configuration), the time required for the output stabilization can be made 1 / m.

  In the particle detection sensor 100, the use of a VCSEL for the light emitting element 110 is preferable because a multi-beam light source can be realized as an element with a small area and the productivity is also high. Further, the VCSEL has an advantage that the beam separation is easy because the light emitting point is small and the beam spot is easy to be narrowed. For example, a general light source, LED (Light Emitting Diode), has a large light emitting point and can not sufficiently narrow a beam spot at a focusing point, so that when a plurality of particles cross light beams, they are separated. Can not be detected as a single particle.

  In addition, since the light source of the LED light source can not sufficiently narrow the light beam at the beam spot, the output fluctuation becomes large depending on how the light beam strikes the fine particles. Specifically, when the fine particles hit the center of the light beam having a large light amount, the light amount of the scattered light also increases, but when the fine particles hit the periphery of the light beam having a small light amount, the light amount of the scattered light also decreases. For this reason, in a conventional particulate matter detection sensor using an LED light source as a light emitting element, as shown in FIG. 3, a detection signal (an electrical signal outputted from a light receiving element) obtained by detecting scattered light is sampled and Accumulation of portions where the sampling signal exceeds a predetermined threshold is integrated, and the integration information is counted. However, the width of the area in which the sampling signal is counted fluctuates depending on the position of the particle with respect to the beam spot, which causes a problem that the output fluctuation becomes large.

  On the other hand, when a VCSEL is used for the light emitting element 110, the frequency of the fully focused light beam hits the particles more frequently. For this reason, the detection signal output from the light receiving element 130 is less likely to fluctuate depending on the position of the particle with respect to the beam spot. In addition, when a VCSEL is used as the light emitting element 110, the control unit 140 samples a detection signal, and counts a portion where the sampling signal exceeds a predetermined threshold. In this detection method, by making the pulse width of the light beam L narrower than in the case of using the LED light source, the count of the sampling signal becomes stable, so the output of the particle detection sensor 100 becomes more stable.

Second Embodiment
The particle detection sensor 100 shown in the first embodiment exemplifies a configuration provided with one condensing lens 120 as an optical system for condensing the light beam L emitted from the light emitting element 110 toward the detection region R. However, the present invention is not limited to this. That is, the optical system for condensing the light beam L toward the detection area R may be a combination of a plurality of lenses.

  FIG. 4 is a schematic view showing the basic configuration of the particle detection sensor 101 according to the second embodiment. The particle detection sensor 101 has a configuration substantially similar to that of the particle detection sensor 100 shown in FIG. 1, but a condensing lens as an optical system for condensing the light beam L emitted from the light emitting element 110 toward the detection region R The difference is that the adjusting lens 121 is added in addition to 120. Specifically, a concave lens is used as the adjustment lens 121 so that the beam separation area can be taken large.

  In the particle detection sensors 100 and 101, the detection region R is set only in the condensing point of the light beam L and a partial region before and after that. This occurs because the light beam L is not sufficiently narrowed in the area away from the light beam L focusing point, and thus the light beam L is irradiated to fine particles such as dust in such an area. This is because the light amount of the scattered light L ′ is too small to be detected by the light receiving element 130.

  Further, like the particle detection sensor 100, the particle detection sensor 101 has a particle passage hole (not shown) in a part of the housing, takes in particles in the passage hole, and enters the inside of the passage hole. The detection area R is configured to exist.

  In the particle detection sensor 101, the adjustment lens 121 is added in addition to the condensing lens 120, so that the light beam L transmitted through the condensing lens 120 can be narrowed longer. That is, in the optical system having the condensing lens 120 and the adjusting lens 121, the light beam L crossing the detection area R can be narrowed narrowly, and even if it is not the condensing point of the light beam L, particles can be detected. The detection probability is further increased, and the output can be stabilized in a short time.

Third Embodiment
In the particle detection sensors 100 and 101, the light emitting element 110 is a multi-beam light source. In the third embodiment, the arrangement of the light emitting points 110b on the light emitting surface 110a of the light emitting element 110 will be described with reference to FIGS. 5 (a) to 5 (c).

  In the present invention, the arrangement of the light emitting points 110b in the light emitting element 110 is basically not particularly limited, and can be, for example, a two-dimensional matrix arrangement as shown in FIG. 5 (a). On the other hand, the outputs of the particle detection sensors 100 and 101 can be made more stable by devising the arrangement of the light emitting points 110b.

  FIGS. 5B and 5C show the arrangement of the light emitting points 110 b for further stabilizing the outputs of the particle detection sensors 100 and 101. In the configuration shown in FIG. 5B, the light emitting points 110b are concentrically arranged on the light emitting surface 110a of the light emitting element 110. In the configuration shown in FIG. 5C, in the light emitting surface 110a of the light emitting element 110, the adjacent light emitting points 110b are arranged so as to be the vertices of an equilateral triangle.

  In the arrangement shown in FIGS. 5 (b) and 5 (c), the arrangement intervals of the plurality of light emitting points 110b are more uniform than in the matrix arrangement shown in FIG. 5 (a). The probability of passing the beam spot is less likely to change. As a result, the outputs of the particle detection sensors 100 and 101 become more stable. The optimal arrangement of the light emitting points 110b is the concentric arrangement shown in FIG. 5 (b).

  In addition, it is preferable that the particle detection sensors 100 and 101 described above basically have the light emitting element 110 be pulse-lit. This is because it takes time to stabilize the output in the conventional pulse lighting drive, and the present invention is effective for solving the problem. However, the present invention is not limited to this, and the present invention is also applicable to one that causes the light emitting element 110 to emit light constantly.

  The present invention is not limited to the above-described embodiments, and various modifications can be made within the scope of the claims, and embodiments obtained by appropriately combining the technical means disclosed in the different embodiments. Is also included in the technical scope of the present invention.

100, 101 particle detection sensor 110 light emitting element 110a light emitting surface 110b light emitting point 120 condensing lens 121 adjusting lens 130 light receiving element 140 control unit L light beam (output light)
R detection area P fine particle L 'scattered light

Claims (6)

A particle detection sensor, which irradiates output light from a light emitting element to a detection area and detects scattered light generated by hitting particles in the detection area with a light receiving element,
The particulate matter detection sensor according to claim 1, wherein the light emitting element is a multi-beam light source having a plurality of light emitting points on a light emitting surface. The particulate matter detection sensor according to claim 1, wherein
The particulate matter detection sensor according to claim 1, wherein the output light from each light emitting point of the light emitting element is a pulse light. The particulate matter detection sensor according to claim 1 or 2, wherein
The particulate matter detection sensor, wherein the light emitting element is a VCSEL. The particulate matter detection sensor according to any one of claims 1 to 3, wherein
A particulate matter detection sensor comprising an optical system for condensing output light emitted from the light emitting element toward the detection area. The particulate matter detection sensor according to claim 4, wherein
The particulate matter detection sensor according to claim 1, wherein the optical system comprises a condenser lens for condensing the output light, and an adjustment lens for adjusting the output light transmitted through the condenser lens in a more elongated manner. The particulate matter detection sensor according to any one of claims 1 to 5, wherein
In the light emitting element, the plurality of light emitting points are arranged concentrically.

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