TW201939009A - Particle detecting sensor - Google Patents

Abstract

This particle detecting sensor (1) detects particles contained in a fluid of interest, and is provided with: a light projecting unit (20) which emits light (L1) toward a detection area (DA); a light receiving unit (30) which has light-receiving sensitivity with respect to the light emitted by the light projecting unit (20), and which generates and outputs an electrical signal by performing photoelectric conversion of scattered light (L2) originating from the light (L1), caused by a particle passing through the detection area (DA); a signal processing circuit (50) which, on the basis of the electrical signal, calculates a first mass concentration of a first particle category including a first particle, and a second mass concentration of a second particle category including the first particle and a second particle larger than the first particle; and a correcting circuit (60) which estimates the number of second particles on the basis of the number of first particles, and corrects the second mass concentration on the basis of the estimated number of particles.

Description

Particle detection sensor

The invention relates to a particle detection sensor.

Conventionally, there is known a photoelectric particle detection sensor including a light-emitting element and a light-receiving element that detects particles floating in the air and calculates the particle diameter of the detected particles (for example, refer to Patent Document 1).
[Prior technical literature]
[Patent Literature]

[Patent Document 1] Japanese Patent Laid-Open No. 2015-210183

[Problems to be solved by the invention]

In the photoelectric particle detection sensor, the mass concentration of each particle size can be calculated according to the particle size and the number of particles. In this case, in order to calculate the mass concentration with sufficient accuracy, it is necessary to obtain the number of particles having a specific number or more. However, in general, as the particle diameter increases, the number of particles floating in the atmosphere decreases. Therefore, there is a problem that the measurement accuracy of the mass concentration of the so-called large particle size is deteriorated.

Therefore, an object of the present invention is to provide a particle detection sensor that can accurately measure the mass concentration of a plurality of particle sizes.

[Technical means to solve the problem]
In order to achieve the above object, a particle detection sensor according to the present invention is one that detects particles contained in a target fluid, and includes: a light-emitting portion that emits light toward a detection area; and a light-receiving portion that emits light to the light-emitting portion. The light has photosensitivity, and an electrical signal is generated and output by photoelectrically converting the scattered light of the light caused by particles passing through the detection area; a signal processing circuit calculates a first signal including the first particle based on the electrical signal. 1 first mass concentration of particle size division, and second mass concentration of second particle size division including the first particle and second particle larger than the first particle; and a correction circuit based on the particle of the first particle The number of particles of the second particles is estimated, and the correction of the second mass concentration is performed based on the estimated number of particles.
[Effect of the invention]

According to the particle detection sensor of the present invention, it is possible to accurately measure the mass concentration of a plurality of particle sizes.

Hereinafter, a particle detection sensor according to an embodiment of the present invention will be described in detail using drawings. It should be noted that the embodiments described below are all specific examples of the present invention. Therefore, the numerical values, shapes, materials, constituent elements, arrangement of constituent elements, and configuration of the constituent elements, steps, and order of the steps shown in the following embodiments are examples and are not intended to limit the present invention. Therefore, among the constituent elements of the following embodiments, constituent elements not described in the independent technical solution will be described as arbitrary constituent elements.

In addition, each figure is a schematic diagram, and is not strictly illustrated. Therefore, for example, the scale of each figure may not be the same. In addition, the same reference numerals are assigned to substantially the same components in the drawings, and repeated descriptions are omitted or simplified.

(Implementation form)
[Composition]
First, the particle detection sensor 1 according to the embodiment will be described using FIGS. 1 to 3.

FIG. 1 is a perspective view of a particle detection sensor 1 according to this embodiment. FIG. 2 is a cross-sectional view of the particle detection sensor 1 according to this embodiment. Specifically, FIG. 2 shows a cross section parallel to the XY plane at the approximate center of the Z-axis direction of the casing 10 of the particle detection sensor 1. FIG. 3 is an enlarged sectional view for explaining the operation of the particle detection sensor 1 according to this embodiment. Specifically, FIG. 3 is an enlarged view of a portion including the detection area DA in the cross-section shown in FIG. 2.

In addition, the X-axis, Y-axis, and Z-axis systems show three axes of a three-dimensional orthogonal coordinate system. The X-axis direction and the Y-axis direction are directions along two sides of the casing 10 having a substantially flat rectangular parallelepiped shape. The Z-axis direction corresponds to the thickness direction of the casing 10.

The particle detection sensor 1 is a photoelectric type particle detection sensor that detects a plurality of particles P contained in a fluid to be detected. In this embodiment, the target fluid is a gas such as air (air). The particles P are micron-sized fine particles floating in the gas, that is, particulate matter (aerosol). Specifically, the particles P are PM2.5, suspended particulate matter (SPM: Suspended Particulate Matter), PM10, and the like.

As shown in FIG. 1, the particle detection sensor 1 includes a case 10. As shown in FIG. 2, the particle detection sensor 1 includes a light projecting section 20, a light receiving section 30, an induction device 40, a signal processing circuit 50, and a correction circuit 60.

In the cross section shown in FIG. 2, the signal processing circuit 50 and the correction circuit 60 are not shown. Therefore, in FIG. 2, the signal processing circuit 50 and the correction circuit 60 are shown schematically. The signal processing circuit 50 and the correction circuit 60 are, for example, mounted on the outer surface of the housing 10, that is, the surface opposite to the surface on which the inflow port 11 and the outflow port 12 are provided.

The housing 10 houses the light projecting section 20 and the light receiving section 30 and has a detection area DA inside. The casing 10 forms a flow path of a gas including a plurality of particles P. The detection area DA is located on the flow channel of the gas.

Specifically, as shown in FIG. 1, the casing 10 has an inflow port 11 through which gas flows into the inside, and an outflow port 12 through which the gas flows into the outside. As shown by the thick dashed arrow in FIG. 2, the path from the inflow port 11 to the outflow port 12 inside the casing 10 corresponds to the flow path of the gas. FIG. 2 shows an example where the gas flow path is formed in an L shape, but the gas flow path may be formed in a straight line connecting the inflow port 11 and the outflow port 12.

The housing 10 has, for example, light-shielding properties, and suppresses light other than the cause of noise from entering the light receiving unit 30 and the detection area DA. The case 10 is formed by, for example, injection molding using a black resin material. Specifically, the casing 10 is configured by combining a plurality of parts formed by injection molding. The light projecting section 20 and the light receiving section 30 are clamped by the plurality of parts and fixed to a specific position in the casing 10.

A light-capturing structure that is attenuated by multiple reflections of stray light may be provided inside the housing 10. The stray light is light other than the scattered light L2 (see FIG. 3) among the light L1 (see FIG. 3) emitted from the light projecting section 20 and is not scattered by the particles P passing through the detection area DA. The light-capturing structure can also attenuate the light incident from the inflow port 11 or the outflow port 12 to the outside.

The light projecting unit 20 emits light L1 toward the detection area DA. As shown in FIGS. 2 and 3, the light projection unit 20 includes a light projection element 21 and a lens 22.

The light projection element 21 is, for example, a solid-state light-emitting element, and specifically, a laser element such as a semiconductor laser. Alternatively, the light projection element 21 may be a light emitting diode (LED: Light Emitting Diode) or an organic EL (Electroluminescence) element.

The light L1 emitted from the light projection element 21 is infrared light, ultraviolet light, blue light, green light, or red light that is equal to light having a peak at a specific wavelength. The half-width at the peak of the light L1 may be a narrow frequency band such as 50 nm or less. The light L1 is continuous light or pulse light driven by DC, but it is not limited to this.

The lens 22 is disposed between the light projection element 21 and the detection area DA. The lens 22 is, for example, a condenser lens, and efficiently focuses the light L1 emitted from the light projection element 21 on the detection area DA.

The light-receiving unit 30 has a light-receiving sensitivity to the light emitted from the light-projecting unit 20, and generates and outputs an electrical signal by photoelectrically converting the scattered light L2 of the light L1 caused by the particles P passing through the detection area DA. As shown in FIGS. 2 and 3, the light receiving unit 30 includes a light receiving element 31 and a lens 32.

The light receiving element 31 is, for example, a photoelectric conversion element that converts received light into an electrical signal, such as a photodiode, a photocrystal, or a photomultiplier tube. The light receiving element 31 outputs an electric signal corresponding to the received light intensity of the received light. The light receiving element 31 has sensitivity in a wavelength band of the light L1 emitted from the light projecting element 21.

As shown in FIG. 2, the light receiving element 31 is disposed at a position where the light L1 emitted from the light projection element 21 is not directly incident. Specifically, the light receiving element 31 is disposed at a position that does not overlap the optical axis of the light projecting element 21. The optical axis of the light-emitting element 21 corresponds to the path of the strongest light among the light L1 emitted from the light-emitting element 21. Specifically, the optical axis of the light projection element 21 corresponds to a straight line connecting the light projection element 21 and the detection area DA. In this embodiment, the light receiving element 31 is arranged such that the optical axis of the light receiving element 31 intersects the optical axis of the light projecting element 21 at the detection area DA.

The lens 32 is disposed between the light receiving element 31 and the detection area DA. The lens 32 efficiently focuses the scattered light L2 scattered by the particles P in the detection area DA on the light receiving element 31.

The induction device 40 is a device for inducing a target fluid toward the detection area DA. Specifically, the induction device 40 is a blower mechanism that generates an air flow passing through the detection area DA. The induction device 40 is a heating element such as a heater, and generates an updraft caused by heat generation. In addition, in order to use the updraft efficiently, in this embodiment, the particle detection sensor 1 is such that the positive Y-axis direction shown in FIGS. 1 and 2 is vertically upward and the negative Y-axis direction is vertically downward. Use upright.

The induction device 40 may be a small fan or the like. The induction device 40 is disposed inside the casing 10 or may be disposed outside the casing 10.

The signal processing circuit 50 calculates a mass concentration for each particle size division based on an electrical signal output from the light receiving section 30. Specifically, the signal processing circuit 50 calculates a first mass concentration of the first particle size division including the first particle and a second particle size division including the first particle and the second particle larger than the first particle based on the electrical signal. The second mass concentration.

The first particles are specifically minute particles, that is, particles having a particle diameter of, for example, 2.5 μm or less. In this embodiment, the first particle size is classified as a small particle size such as PM2.5, and the first mass concentration is the mass concentration of PM2.5.

The second particle is specifically a coarse particle having a larger particle size than that of the minute particle, that is, a particle having a particle size of, for example, 10 μm or less. In this embodiment, the second particle size is classified as a large particle size such as PM10, and the second mass concentration is the mass concentration of PM10. The second particle size classification may be SPM, and the second mass concentration may also be the mass concentration of SPM.

The signal processing circuit 50 measures the number of particles and the particle size based on the peak size of the electrical signal output from the light receiving unit 30, and calculates the mass concentration of each particle size division based on the measurement result. Specifically, the signal processing circuit 50 estimates the particle diameter of the detected particles by comparing the peak value of the electrical signal with a threshold value of 1 or more that is determined in advance so as to correspond to the particle diameter.

In this embodiment, the signal processing circuit 50 calculates the mass concentration of PM2.5 based on the first signal of the first period amount in the electrical signal, and calculates the mass concentration of PM10 based on the second signal of the second period amount in the electrical signal. The first period is, for example, a measurement period of the number of particles (hereinafter referred to as the number of PM2.5 particles) of fine particles included in PM2.5. The second period is a period different from the first period, that is, the measurement period of the number of particles of coarse particles included in PM10 (hereinafter referred to as the number of PM10 particles).

That is, in the particle detection sensor 1 of this embodiment, the measurement of the number of PM2.5 particles and the measurement of the number of PM10 particles are performed in a time-sharing manner. Specifically, the signal processing circuit 50 divides and calculates the electrical signal output from the light receiving unit 30 into each specific period, and measures the number of particles for each particle size.

At this time, the signal processing circuit 50 causes the amplification factor (gain) of the electrical signal output from the light receiving element 31 to differ depending on the particle size of the object to be measured. Specifically, as shown in FIG. 4, the signal processing circuit 50 includes two amplifiers 51 and 52 and a switch 53.

FIG. 4 is a diagram showing the configuration of a signal processing circuit 50 according to this embodiment. As shown in FIG. 4, the signal processing circuit 50 further includes three resistors 54 to 56 and an arithmetic circuit 57. The signal processing circuit 50 has a multi-stage configuration including two amplifiers 51.

The amplifiers 51 and 52 are, for example, operational amplifiers. A light receiving element 31 is connected between the positive input terminal and the negative input terminal of the amplifier 51. An output terminal of the amplifier 51 is connected to a negative input terminal via a resistor 54. An output terminal of the amplifier 51 is further connected to a positive input terminal of the amplifier 52.

The negative input terminal of the amplifier 52 is grounded via a resistor 55. The output terminal of the amplifier 52 is connected to the negative input terminal via a resistor 56. An output terminal of the amplifier 52 is connected to the arithmetic circuit 57.

The switch 53 is provided in parallel with respect to the resistor 56, that is, between the output terminal and the negative input terminal of the amplifier 52. When the switch 53 is turned on (turned on), the output terminal of the amplifier 52 and the negative input terminal are short-circuited, so that the amplification of the amplifier 52 is not performed. When the switch 53 is turned on, only the amplification of the amplifier 51 is performed. In this way, the amplification of the electrical signals can be made different by turning on / off the switch 53.

Specifically, the signal processing circuit 50 increases the magnification by turning off the switch 53 in the first period of measuring the number of PM2.5 particles. For example, when the magnitude of the photocurrent output from the light receiving element 31 is set to I and the voltage of the output signal of the amplifier 52 is set to Vout, the following formula (1) represents Vout when the switch 53 is turned off.

(1) Vout = Z ₁ × (1 + Z ₃ / Z ₂ ) × I

Z ₁ to Z ₃ are resistance values of resistances 54 to 56 respectively. The magnification is represented by Z ₁ × (1 + Z ₃ / Z ₂ ).

When measuring the number of PM2.5 particles, since the particles reflecting the light from the light projection element 21 are fine particles, the scattered light L2 of the particles is weakened. Therefore, the photocurrent output from the light receiving element 31 is reduced. Therefore, the voltage of the output signal can be increased by turning off the switch 53 and increasing the amplification factor. Thereby, it is easy to compare the peak value with the threshold value, and the particle diameter can be estimated with high accuracy.

The signal processing circuit 50 is in a second period for measuring the number of PM10 particles, and the switch 53 is turned on to reduce the amplification factor. The following formula (2) represents Vout when the switch 53 is turned on.

(2) Vout = Z ₁ × I

In the case of measuring the number of PM10 particles, since the particles reflecting the light from the light-emitting element 21 are coarse particles, the scattered light L2 is enhanced compared with the fine particles. Therefore, the photocurrent output from the light receiving element 31 also increases. Therefore, the switch 53 can be turned on to reduce the amplification factor.

In this way, the magnification can be made different depending on the particle size of the measurement object, and the range of Vout that can be taken is made equal regardless of the particle size of the measurement object. This makes it possible to easily compare the peak value of the arithmetic circuit 57 at the subsequent stage with the threshold value.

In this embodiment, the arithmetic circuit 57 estimates the particle size of the particles based on the maximum value of the peak value (hereinafter referred to as the peak value) indicated by the electrical signal in the first period of time to measure the number of PM2.5 particles, and classifies the particles into a plurality of sub-particles. Any one of them. The subdivision of PM2.5 is a plurality of subdivisions divided by a particle size equivalent to PM2.5 based on a threshold of 1 or more.

FIG. 5 is a diagram showing an electrical signal output from the light receiving element 31 of the particle detection sensor 1 according to this embodiment, that is, a first signal during a first period of measuring the number of PM2.5 particles. In FIG. 5, the horizontal axis represents time, and the vertical axis represents the signal strength of the electrical signal. In this embodiment, since the electrical signal output from the light receiving element 31 is converted into a voltage Vout, the vertical axis corresponds to a voltage value.

For example, as shown in FIG. 5, PM2.5 is divided into 4 sub-divisions based on 4 thresholds 1 to 4. Specifically, PM2.5 includes, for example, the first subdivision of 1.0 μm or more, the second subdivision of less than 1.0 μm and 0.5 μm or more, the third subdivision of less than 0.5 μm and 0.3 μm or more, and the third subdivision of less than 0.3 μm. 4 sub distinctions. In addition, the threshold 4 is a threshold for removing noise components.

FIG. 5 shows an example in which five peaks S1 to S5 appear. The peak values S1 to S5 are equivalent to changes in electrical signals that are displayed by the light receiving element 31 by receiving the scattered light L2 caused by particles passing through the detection area DA. The arithmetic circuit 57 compares the peak value and the threshold value of each of the peak values S1 to S5 to classify the particles into any one of the first subdivision to the fourth subdivision of PM2.5.

For example, since the peak value of the peak S1 is smaller than the threshold value 2 and equal to or greater than the threshold value 3, particles corresponding to the peak value S1 are classified as the third sub-division. Similarly, since the peak value of the peak S2 is smaller than the threshold value 3 and equal to or greater than the threshold value 4, the particles corresponding to the peak value S2 are classified as the fourth sub-division. Since the peak value of the peak S3 is smaller than the threshold value 1 and equal to or greater than the threshold value 2, the particles corresponding to the peak value S3 are classified as the second sub-division. Since the peak value of each of the peak values S4 and S5 is equal to or greater than the threshold value 1, particles corresponding to each of the peak values S4 and S5 are classified as the first sub-division.

The same applies to PM10. Specifically, the arithmetic circuit 57 estimates the particle size of the particle based on the maximum value (peak value) of the peak value appearing in the electrical signal of the second period of time when the number of PM10 particles is measured, and classifies it into any one of a plurality of subdivisions. . The subdivision of PM10 is a plurality of subdivisions divided by a particle size equivalent to PM10 based on a threshold of 1 or more.

FIG. 6 is a diagram showing an electrical signal output from the light receiving element 31 of the particle detection sensor 1 according to this embodiment, that is, a second signal during the second period of measuring the number of PM10 particles. In FIG. 6, the horizontal axis represents time, and the vertical axis represents the signal strength of the electrical signal. In this embodiment, since the electrical signal output from the light receiving element 31 is converted into a voltage Vout, the vertical axis corresponds to a voltage value.

For example, as shown in FIG. 6, PM10 is divided into four sub-divisions based on four thresholds A to D. Specifically, PM10 includes, for example, a first subdivision smaller than 10 μm and greater than 5 μm, a second subdivision smaller than 5 μm and greater than 2.5 μm, a third subdivision smaller than 2.5 μm and greater than 1.0 μm, and less than 1.0 μm. The fourth subdivision.

FIG. 6 shows an example in which five peaks Sa to Se appear. The peaks Sa to Se respectively correspond to changes in electrical signals that are displayed by the light receiving element 31 by receiving the scattered light L2 caused by particles passing through the detection area DA. The arithmetic circuit 57 compares the peak value of each of the peaks Sa to Se with a threshold value to classify the particles into any one of the first sub-section to the fourth sub-section of PM10. The specific treatment is the same as in the case of PM2.5.

In addition, the number of child divisions of at least one of PM2.5 and PM10 is not limited to four, but may be two or three, and may be five. Alternatively, the number of subdivisions may be one. That is, at least one of PM2.5 and PM10 may not be divided into a plurality of subdivisions.

In addition, the particle detection sensor 1 of the present embodiment actually includes a plurality of particles passing through a portion other than the center of the detection area DA. For example, when a larger particle passes the end of the detection area DA, the intensity of the scattered light received by the light receiving element 31 due to the particle decreases. Therefore, even if it is a large particle, there is a possibility that the size of the particle is erroneously determined as "small".

In order to suppress this erroneous determination, the arithmetic circuit 57 of this embodiment maintains a histogram in memory corresponding to the signal intensity (voltage value) and the particle frequency of particles of each size, as shown in FIG. 7. FIG. 7 is a histogram of particles detected by the particle detection sensor 1 of this embodiment. In FIG. 7, the horizontal axis is the signal intensity, and the vertical axis is the frequency of particles of particles of each size.

As shown in FIG. 7, when the signal intensity is large, particles having a large particle diameter are basically used. On the other hand, when the signal intensity is small, in addition to particles having a small particle diameter, particles having a large particle diameter and passing through a portion other than the center of the detection area DA are also included. The calculation circuit 57 estimates the size of the particle P corresponding to the peak value by referring to the histogram shown in FIG. 7 based on the peak intensity of the electrical signal.

The arithmetic circuit 57 counts the number of particles P detected during a specific operation period for each sub-division. The arithmetic circuit 57 calculates the product of the predetermined average mass and the counted number for each subdivision, and adds the calculated product of each subdivision, thereby calculating the mass concentration of PM2.5 and the mass concentration of PM10, respectively.

The arithmetic circuit 57 is implemented by, for example, one or more electronic components including a comparator and the like. For example, the arithmetic circuit 57 may be implemented by an MPU (Micro Processing Unit). The processing performed by the arithmetic circuit 57 may be implemented in hardware, and may also be implemented in software executed by a processor.

The correction circuit 60 estimates the number of particles of the second particle included in the second particle size division based on the number of particles of the first particles included in the first particle size division, and performs a mass concentration determination of the second particle diameter based on the estimated number of particles. Amended. Specifically, the correction circuit 60 estimates the number of coarse particles included in PM10 based on the number of particles included in PM2.5. The correction circuit 60 corrects the mass concentration of PM10 based on the estimated number of coarse particles.

In this embodiment, the number of particles of the minute particles is the number of particles included in the sub-division with the largest particle size among the plurality of sub-divisions obtained by dividing PM2.5. For example, the number of fine particles in the example shown in FIG. 5 is the number of particles included in the fourth subdivision having a particle diameter of 1.0 μm or more.

The correction circuit 60 estimates the number of coarse particles based on the content ratio of the number of particles included in the fourth subdivision. The content rate corresponds to the ratio of the number of particles included in the fourth subdivision to the total number of particles equivalent to PM2.5.

In this embodiment, the correction circuit 60 performs approximately two types of correction. The two types of corrections are a first correction that corrects the mass concentration of PM10 calculated by the signal processing circuit 50 and a second correction that is a measurement method for adjusting the number of PM10 particles. Details of each correction process will be described later.

The correction circuit 60 is realized by, for example, one or more electronic components. For example, the correction circuit 60 may be implemented by an MPU or the like. The actions performed by the correction circuit 60 may be implemented in hardware or in software executed by a processor.

[Correction circuit]
The correction processing performed by the correction circuit 60 will be described below.

First, the first correction for correcting the mass concentration of PM10 will be described using FIG. 8. FIG. 8 is a graph showing the concentration distribution with respect to the particle size of each of PM2.5 and PM10. In FIG. 8, the horizontal axis represents the particle diameter [μm], and the vertical axis represents the mass concentration.

As shown in FIG. 8, there is a overlapped portion (shaded portion) between the PM2.5 concentration distribution and the PM10 concentration distribution. The repeated portion is, for example, a portion corresponding to the fourth sub-division of PM2.5.

There is a correlation between the concentration distribution of PM2.5 and the concentration distribution of PM10. Therefore, the particle number of the coarse particles included in PM10 can be estimated based on the content rate corresponding to the number of particles included in the fourth subdivision of the repetitive portion. For example, the correction circuit 60 has a memory that stores correspondence information indicating a correspondence relationship between the content rate and the number of particles of coarse particles. The correction circuit 60 reads the corresponding information from the memory and refers to the read corresponding information, thereby estimating the coarse particles based on the content ratio of the number of particles of the small particles.

The correction circuit 60 corrects the mass concentration of PM10 calculated by the arithmetic circuit 57 based on the estimated number of coarse particles. For example, when the correction circuit 60 is different from the mass concentration based on the estimated number of particles and the mass concentration calculated based on the measurement result (that is, the measured number) of PM10 particles, the correction circuit 60 uses the estimated result by It is averaged with the actual measurement result and output as the correction value of the mass concentration of PM10. In addition, the correction value may not be the average of the estimation result and the actual measurement result, but may be a weighted addition value that strongly weights the estimation result, for example.

In addition, correspondence information corresponding to the estimated number of coarse particles and the correction value of the mass concentration can also be stored in the memory. The correction circuit 60 may also read the corresponding information from the memory, and refer to the read corresponding information, thereby determining and outputting a correction value of the mass concentration according to the estimated number of particles. The correspondence information can be generated in advance, for example, by obtaining an estimated value based on the number of PM2.5 particles under an environment where the mass concentration of PM10 is determined.

Next, the details of the second modification of the method for measuring the number of particles will be described.

＜ Correction during measurement (first example) ＞
First, a first example of the correction of the measurement processing of the number of particles will be described using FIG. 9.

FIG. 9 is a diagram showing an example of adjustment of the measurement period of the number of coarse particles as a first example of the modification of the particle detection sensor 1 according to this embodiment. The correction circuit 60 changes the length of the second period, which is the measurement period of the number of PM10 particles, based on the estimated number of coarse particles.

In the particle detection sensor 1 of this embodiment, as shown in FIG. 9, the measurement of the number of fine particles, the measurement of the number of coarse particles, the calculation of the mass concentration of PM2.5, and the calculation of PM10 Calculation of mass concentration. The measurement of the number of fine particles corresponds to the first period for calculating the mass concentration of PM2.5. The measurement of the number of coarse particles corresponds to the second period for calculating the mass concentration of PM10.

In the present embodiment, as shown in FIG. 9, the correction circuit 60 extends the second period when the estimated number of particles is small compared to when the estimated number of particles is large. This makes it easy to ensure the number of detected coarse particles (the number of detections) is a specific number or more, so that the number of coarse particles can be accurately measured, and the mass concentration of PM10 can be accurately calculated.

When the estimated number of particles is large, even if the second period is not extended, the number of detection of coarse particles with a specific number or more can be ensured. Therefore, the number of coarse particles can be accurately measured, and the mass concentration of PM10 can be accurately calculated. In addition, the time required to measure the number of particles to calculate the mass concentration can be shortened.

＜ Correction of the average number of cycles (second example) ＞
Next, a second example of the correction of the measurement processing of the number of particles will be described using FIG. 10.

FIG. 10 is a diagram showing an example of the adjustment of the average number of cycles when calculating the mass concentration as a second example of the modification of the particle detection sensor 1 according to this embodiment. The correction circuit 60 changes the average number of cycles when calculating the mass concentration of PM10 based on the estimated number of coarse particles.

In the particle detection sensor 1 of this embodiment, as shown in FIG. 10, the measurement of the number of particles of a small particle, the measurement of the number of particles of a coarse particle, calculation of the mass concentration of PM2.5, and calculation of the mass concentration of PM10 are set as 1 cycle and repeat the cycle multiple times. The mass concentration was calculated by averaging the mass concentration calculated every cycle.

Specifically, the arithmetic circuit 57 repeats the process of calculating the mass concentration of PM10 based on the electrical signal (second signal) obtained during the coarse particle measurement period for a specific number of times, and averages the mass concentration of the specific number of times obtained, thereby Calculate the mass concentration of PM10. The correction circuit 60 changes the number of averaging, that is, the number of cycles.

In this embodiment, as shown in FIG. 10, the correction circuit 60 increases the number of cycles when the estimated number of particles is small compared to when the estimated number of particles is large. For example, in FIG. 10, when the number of estimated particles is large, the number of cycles is three times. In contrast, when the number of estimated particles is small, the number of cycles is six times. A specific numerical example of the number of cycles is not limited to this.

With this, under the assumption of averaging, it is easy to ensure that the number of coarse particles detected (detected number) is a certain number or more. Therefore, the number of coarse particles can be accurately measured and the mass concentration of PM10 can be accurately calculated. .

The same applies to the case where the calculation circuit 57 is in the mass concentration of PM2.5. At this time, the average number of cycles can be the same at PM2.5 and different at PM10. For example, the number of cycles at PM2.5 may always be specified regardless of the estimated number of particles.

＜ Correction of correction amount (third example) ＞
Next, a third example of the correction of the measurement processing of the number of particles will be described using FIG. 11.

FIG. 11 is a diagram showing an example of adjustment of the amount of induction of the target fluid as a third example of the modification of the particle detection sensor 1 according to this embodiment. The correction circuit 60 changes the amount of induction of the target fluid induced by the induction device 40 during the second period of measurement of the coarse particles.

In this embodiment, the induction device 40 is a blower for introducing gas into the inside of the casing 10. Therefore, the correction circuit 60 changes the inspiratory amount to the induced amount. For example, when the induction device 40 is a resistive element and utilizes a rising airflow that generates heat, the correction circuit 60 adjusts the amount of heat generated by adjusting the current flowing through the resistive element. For example, the correction circuit 60 can increase the flow of air and increase the amount of heat to increase the updraft and increase the amount of air intake.

As shown in FIG. 11, when the number of estimated particles is small, the correction circuit 60 increases the amount of air intake compared with the case where the number of estimated particles is large. Thereby, since the amount of gas introduced in one measurement increases, the number of particles contained in the gas can also be increased. Therefore, it is possible to ensure the number of detection of coarse particles of a specific number or more. Therefore, the number of coarse particles can be accurately measured, and the mass concentration of PM10 can be accurately measured.

In the second modification of the method for measuring the number of PM10 particles, all of the first to third examples described above may be performed, and only one may be performed. In addition, both of the second correction of the measurement method of the number of PM10 particles and the first correction of the mass concentration of PM10 may be performed, or only one of them may be performed.

[Effects, etc.]
As described above, the particle detection sensor 1 according to this embodiment is a particle detection sensor that detects particles contained in a target fluid, and includes: a light projecting section 20 that emits light toward a detection area DA; and a light receiving section 30 It has a light receiving sensitivity to the light L1 emitted from the light projecting part 20, and generates and outputs an electrical signal by photoelectrically converting the scattered light L2 of the light caused by the particles passing through the detection area DA. The particle detection sensor 1 further includes a signal processing circuit 50 that calculates a first mass concentration (for example, a mass concentration of PM2.5) of the first particle size division including the fine particles based on the electrical signal, and includes the fine particles and a concentration greater than The second mass concentration (for example, PM10 mass concentration) of the second particle size division of the coarse particles of the fine particles; and a correction circuit 60 that estimates the number of coarse particles based on the number of fine particles and performs the estimation based on the estimated number of particles Correction of the second mass concentration.

Thereby, the number of particles with a specific number or more can be easily measured, and the number of coarse particles can be estimated based on the number of fine particles measured with good accuracy, so the accuracy of estimating the number of coarse particles can also be increased. According to this embodiment, since the mass concentration of PM10 is corrected based on the estimation result, the measurement accuracy of the mass concentration of PM10 is also improved. Therefore, in addition to PM2.5, the mass concentration of PM10 can also be measured with good accuracy. As described above, according to the particle detection sensor 1 of this embodiment, it is possible to accurately measure the mass concentration of a plurality of particle sizes.

In addition, for example, the number of particles of the minute particles is the number of particles included in the largest sub-division among a plurality of sub-divisions into which the first particle size division is divided. The correction circuit 60 estimates the number of coarse particles based on the content ratio of the number of fine particles.

Therefore, since the content ratio of the number of particles divided by the largest particle diameter of PM2.5 has a correlation with the number of coarse particles included in PM10, the number of coarse particles can be accurately estimated based on the correlation. As the estimation accuracy of the number of coarse particles is improved, the measurement accuracy of the mass concentration of PM10 is also improved. Therefore, in addition to PM2.5, the mass concentration of PM10 can also be measured with good accuracy.

For example, the signal processing circuit 50 calculates the mass concentration of PM2.5 based on the first signal of the first period amount in the electrical signal, and calculates based on the second signal of the second period amount that is different from the first period in the electrical signal. Mass concentration of PM10.

Thereby, the mass concentration of PM2.5 and the mass concentration of PM10 can be calculated in time series. Since the measured value of the mass concentration of PM10 can be obtained, the accuracy of the correction is improved. Therefore, in addition to PM2.5, the mass concentration of PM10 can also be measured with good accuracy.

For example, as a correction, the correction circuit 60 corrects the mass concentration of PM10 calculated based on the second signal based on the estimated number of particles.

Thereby, since the calculation result of the mass concentration of PM10 is corrected, the mass concentration of PM10 can be accurately measured.

For example, as a correction, the correction circuit 60 changes the length of the measurement period of the coarse particles based on the estimated number of particles.

Thereby, since the time required for the measurement of coarse particles can be extended, it is easy to ensure the number of coarse particles to a specific number or more. Therefore, in addition to PM2.5, the mass concentration of PM10 can also be measured with good accuracy.

In addition, for example, the signal processing circuit 50 repeats the process of calculating the mass concentration of PM10 based on the second signal a specific number of times, and averages the mass concentrations of the obtained specific number of times, thereby calculating the mass concentration of PM10. As a correction, the correction circuit 60 changes the number of repetitions (that is, the number of cycles).

Thereby, since the averaging period when calculating the mass concentration of PM10 can be extended, it is easy to ensure the number of coarse particles to a specific number or more. Therefore, in addition to PM2.5, the mass concentration of PM10 can also be measured with good accuracy.

In addition, for example, the particle detection sensor 1 further includes an induction device 40 that induces a target fluid toward the detection area DA. As a correction, the correction circuit 60 changes the amount of induction of the target fluid induced by the induction device 40 in the second period.

Thereby, since the amount of gas induced when the number of coarse particles is measured increases, it is easy to ensure the number of coarse particles to be a specific number or more. Therefore, in addition to PM2.5, the mass concentration of PM10 can also be measured with good accuracy.

(other)
As mentioned above, although the particle detection sensor of this invention was demonstrated based on the said embodiment, this invention is not limited to the said embodiment.

For example, in the above embodiment, the case where the target fluid is a gas has been described, but it is not limited to this. The target fluid may be a liquid such as water. The particle detection sensor 1 detects particles contained in a liquid such as water, and calculates a mass concentration. At this time, the particle detection sensor 1 has a waterproof mechanism that prevents the signal processing circuit 50 mounted on the outer surface of the casing 10 from coming into contact with liquid. The waterproof mechanism is, for example, a metal sealing member provided to cover the signal processing circuit 50. This sealing member is fixed to the case 10 without gaps, for example, by welding.

In addition, for example, in the particle detection sensor 1, the measurement of the number of PM10 particles may not be performed. Specifically, the signal processing circuit 50 may sequentially perform measurement of fine particles, calculation of the mass concentration of PM2.5, and calculation of the mass concentration of PM10. In the calculation of the mass concentration of PM10, the mass concentration of PM10 can also be calculated using the number of coarse particles estimated based on the content ratio of the number of fine particles contained in PM2.5.

In addition, for example, the correction circuit 60 may estimate the number of particles of the coarse particles based on the total number of particles of the minute particles included in PM2.5 instead of the sub-division of the maximum particle diameter of PM2.5.

In addition, for example, the particle detection sensor 1 may not include the induction device 40. For example, the particle detection sensor 1 may be configured such that when the airflow flows in a specific direction, the inflow port 11 is located on the upstream side of the airflow and the outflow port 12 is located on the downstream side.

Moreover, in the said embodiment, although the example which each provided the light projection part 20 and the light receiving part 30 was equipped with the lens was shown, it is not limited to this. For example, at least one of the light projecting section 20 and the light receiving section 30 may include a mirror (reflector) instead of a lens.

The particle detection sensor 1 is mounted on various household appliances such as air conditioners, air cleaners, and ventilators. Various household electrical appliances can control their operation based on the mass concentration of particles detected by the particle detection sensor 1. For example, when the mass concentration of particles is greater than a specific threshold, the air purifier can increase the operating intensity (specifically, the air purification power).

In addition, for each embodiment, the forms obtained by implementing various changes that can be conceived by those in this field, or the forms realized by arbitrarily combining the constituent elements and functions in each embodiment within the scope not departing from the spirit of the present invention于 发明。 In the present invention.

1‧‧‧ Particle Detection Sensor

10‧‧‧shell

11‧‧‧ Inlet

12‧‧‧ Outlet

20‧‧‧Projection Department

21‧‧‧light-emitting element

22‧‧‧ lens

30‧‧‧Light receiving section

31‧‧‧ light receiving element

32‧‧‧ lens

40‧‧‧ induction device

50‧‧‧ signal processing circuit

51‧‧‧amplifier

52‧‧‧amplifier

53‧‧‧Switch

54‧‧‧ resistance

55‧‧‧ resistance

56‧‧‧ resistance

57‧‧‧ Operation Circuit

60‧‧‧correction circuit

DA‧‧‧ Detection Area

I‧‧‧Photocurrent

L1‧‧‧light

L2‧‧‧Scattered light

P‧‧‧ Particle

PD‧‧‧Photodiode

S1 ～ S5‧‧‧ peak

Sa ～ Se‧‧‧Peak

Vout‧‧‧Voltage

X‧‧‧ direction

Y‧‧‧ direction

Z‧‧‧ direction

Z ₁ ～ Z ₃ ‧‧‧Resistance

FIG. 1 is a perspective view of a particle detection sensor according to an embodiment.

FIG. 2 is a cross-sectional view of a particle detection sensor according to an embodiment.

FIG. 3 is an enlarged sectional view for explaining the operation of the particle detection sensor according to the embodiment.

FIG. 4 is a diagram showing an example of a signal processing circuit of the particle detection sensor according to the embodiment.

FIG. 5 is a diagram showing an electrical signal output from a light receiving element of the particle detection sensor of the embodiment, that is, a signal during a period when the number of particles of a small particle is measured.

FIG. 6 is a diagram showing an electrical signal output from a light receiving element of the particle detection sensor of the embodiment, that is, a signal during a period when the number of coarse particles is measured.

FIG. 7 is a histogram showing particles detected by the particle detection sensor according to the embodiment.

FIG. 8 is a graph showing the concentration distribution of each particle diameter of PM2.5 and PM10.

FIG. 9 is a diagram showing an example of adjustment of the measurement period of the number of coarse particles as the first example of the operation of the particle detection sensor of the embodiment.

FIG. 10 is a diagram showing an example of the adjustment of the averaged number of cycles when calculating the mass concentration as the second example of the operation of the particle detection sensor of the embodiment.

FIG. 11 is a diagram showing a third example of the operation of the particle detection sensor of the embodiment as an example of adjustment of the amount of induction of the target fluid.

Claims (7)

A particle detection sensor is used for detecting particles contained in a target fluid, and includes: A light projection unit, which emits light toward a detection area; The light-receiving unit has a light-receiving sensitivity to light emitted from the light-projecting unit, and generates and outputs an electrical signal by photoelectrically converting scattered light of the light caused by particles passing through the detection area; A signal processing circuit, based on the electrical signal, calculates the first mass concentration including the first particle size division of the first particle and the second particle size division including the first particle and the second particle size larger than the first particle. 2nd mass concentration; and A correction circuit estimates the number of particles of the second particle based on the number of particles of the first particle, and corrects the second mass concentration based on the estimated number of particles. The particle detection sensor as claimed in item 1, wherein The number of particles of the first particle is the number of particles included in the sub-section of the largest particle size among the plurality of sub-sections into which the first particle size division is divided; and The correction circuit estimates the number of particles of the second particle based on the content ratio of the number of particles of the first particle. A particle detection sensor as claimed in item 1 or 2, wherein The signal processing circuit calculates the first mass concentration based on a first signal in a first period of the electrical signals; and The second mass concentration is calculated based on a second signal of a second period amount different from the first period of the electrical signals. The particle detection sensor of claim 3, wherein The correction circuit corrects the second mass concentration calculated based on the second signal based on the estimated number of particles as the correction. The particle detection sensor of claim 3, wherein The correction circuit changes the length of the second period based on the estimated number of particles as the correction. The particle detection sensor of claim 3, wherein The signal processing circuit repeats the process of calculating the second mass concentration based on the second signal a specific number of times, and averages the mass concentration obtained in a specific number of times, thereby calculating the second mass concentration; and The correction circuit changes the specific number of times as the correction. The particle detection sensor of claim 3, further comprising: An induction device that induces the target fluid toward the detection area; and The correction circuit changes the amount of induction of the target fluid induced by the induction device in the second period as the correction.