JP6830262B2 - Particle detection sensor, dust sensor, smoke detector, and air conditioner - Google Patents

Description

The present invention relates to a particle detection sensor, a dust sensor, a smoke detector, and an air conditioner.

The light scattering type particle detection sensor is a photoelectric sensor including a light emitting element and a light receiving element. It takes in a fluid to be measured, irradiates the fluid with the light of the light scattering element, and contains the scattered light in the fluid. Detects the presence or absence of particles. Such a particle detection sensor can detect particles such as dust, pollen, and smoke floating in the atmosphere (see, for example, Patent Documents 1 to 4).

Japanese Unexamined Patent Publication No. 2015-114176 Japanese Unexamined Patent Publication No. 2006-138833 Japanese Unexamined Patent Publication No. 2001-058114 JP-A-2002-116135

In order to detect from fine particles equivalent to PM2.5 to coarse particles equivalent to pollen (for example, maximum particle diameter 50 μm) using such a particle detection sensor, a circuit that processes an electric signal corresponding to the scattered light intensity. It is necessary to design the dynamic range of the. For example, the scattered light intensity of coarse particles having a particle diameter of 50 μm is approximately 50,000 times the scattered light intensity of fine particles having a particle diameter of 0.3 μm. Therefore, when trying to detect from fine particles to coarse particles, a circuit that processes an electric signal is required to have a similar dynamic range. However, it is very difficult to realize a circuit having such a large dynamic range due to circuit characteristics and the like.

Therefore, the present invention provides a particle detection sensor or the like capable of widening the dynamic range of the particle diameter that can be determined (widening the dynamic range) without increasing the dynamic range of the circuit that processes the electric signal. With the goal.

In order to achieve the above object, the particle detection sensor according to one aspect of the present invention includes a light projecting element that projects light into the detection region and the light projecting by particles passing through the detection region at a speed dependent on the particle size. The higher the frequency of the light receiving element that receives the scattered light of the light from the element and generates an electric signal including the pulsed waveform corresponding to the particle and the electric signal input from the light receiving element, the higher the electric signal. It is provided with an amplifier circuit that amplifies the light with a large amplification factor, and a calculation unit that calculates the particle size of the particles that have passed through the detection region based on the pulse width of the pulsed waveform included in the amplified electric signal.

Further, the particle detection sensor according to another aspect of the present invention is from a light projecting element that projects light into the detection region and the light projecting element that uses particles that pass through the detection region at a speed that depends on the particle size. A light receiving element that receives scattered light and performs photoelectric conversion with higher conversion efficiency as the frequency obtained by the temporal change of the received scattered light increases, and generates an electric signal including a pulsed waveform corresponding to the particle. And an amplifier circuit that amplifies the electric signal input from the light receiving element, and a calculation for calculating the particle size of the particles that have passed through the detection region based on the pulse width of the pulsed waveform included in the amplified electric signal. It has a part.

Further, each of the dust sensor and the smoke detector according to one aspect of the present invention includes the above-mentioned particle detection sensor.

Further, in the air conditioner according to one aspect of the present invention, the particle detection sensor and a flow velocity generating unit that allows a fluid containing the particles to pass through the detection region in a direction that hinders the movement of the particles due to their own weight. Be prepared.

According to the particle detection sensor or the like according to the present invention, it is possible to widen the dynamic range of the particle diameter that can be determined without increasing the dynamic range of the circuit that processes the electric signal.

FIG. 1 is a block diagram showing an example of the configuration of the particle detection sensor according to the embodiment. FIG. 2 is a diagram schematically showing the state of particles in the fluid passing through the detection region. FIG. 3 is a graph showing an outline of the frequency characteristics of the amplification factor of the amplifier circuit. FIG. 4 is a diagram conceptually showing the amplification process by the amplifier circuit. FIG. 5 is a graph showing an electric signal after amplification by an amplifier circuit in Modification 2. FIG. 6 is a graph showing an electric signal after amplification by an amplifier circuit in Modification 3. FIG. 7 is a diagram schematically showing the state of particles in the fluid passing through the detection region in the modified example 4. FIG. 8 is a block diagram showing an example of the configuration of the particle detection sensor according to the modified example 5. FIG. 9 is an external view of an air purifier including a particle detection sensor. FIG. 10 is an external view of a smoke detector including a particle detection sensor. FIG. 11 is an external view of a ventilation fan including a particle detection sensor. FIG. 12 is an external view of an air conditioner including a particle detection sensor.

Hereinafter, the particle detection sensor and the like according to the embodiment of the present invention will be described in detail with reference to the drawings. It should be noted that all of the embodiments described below show a preferred specific example of the present invention. Therefore, the numerical values, shapes, materials, components, arrangement and connection forms of the components, steps and the order of steps shown in the following embodiments are examples, and are not intended to limit the present invention. Therefore, among the components in the following embodiments, the components not described in the independent claims indicating the highest level concept of the present invention will be described as arbitrary components.

Further, each figure is a schematic view and is not necessarily exactly illustrated. Further, in each figure, the same constituent members may be designated by the same reference numerals, and duplicate description may be omitted or simplified.

(Embodiment)
[1. Constitution]
First, the overall configuration of the particle detection sensor according to the embodiment of the present invention will be described.

FIG. 1 is a block diagram showing an example of the configuration of the particle detection sensor 1 according to the present embodiment. In the figure, the internal configuration of the sensor unit 10 is schematically shown.

The particle detection sensor 1 detects particles contained in the air floating around the particle detection sensor 1 (hereinafter, referred to as ambient air).

As shown in the figure, the particle detection sensor 1 includes a sensor unit 10 and a signal processing unit 20, and is attached to the particle detection sensor 1 based on scattered light from the particles 2 located in the detection region DA of the sensor unit 10. Detects particles contained in the captured ambient air. Further, the particle detection sensor 1 further includes a power supply unit 30 that supplies power to each configuration included in the particle detection sensor 1. The power supply unit 30 is composed of, for example, a regulator that converts a voltage supplied from the outside of the particle detection sensor 1 into a desired voltage.

Hereinafter, each configuration of the particle detection sensor 1 will be specifically described.

[1-1. Sensor part]
The sensor unit 10 takes in the ambient air to be measured by the particle detection sensor 1, irradiates the captured ambient air with light, and outputs an electric signal (here, a current signal) indicating the light intensity of the scattered light. It is a photoelectric sensor (light scattering type particle detection sensor). That is, the sensor unit 10 outputs a time-series electric signal corresponding to the particles 2 contained in the captured ambient air.

Specifically, in the present embodiment, the sensor unit 10 includes a light emitting system 11, a light receiving system 12, a housing 13, and a heater 15, and a particle flow from the inlet 18 to the outlet 19 of the housing 13. An electric signal corresponding to the scattered light from the particles 2 passing through the detection region DA provided on the path (located in the detection region DA) is output. The light projecting system 11, the light receiving system 12, and the detection area DA are housed in the housing 13 so as not to be irradiated with external light.

The detection region DA is an aerosol detection region (aerosol measurement unit) for detecting particles 2 (aerosol) contained in the gas to be measured, and includes the optical axis P of the light projecting system 11 and the optical axis Q of the light receiving system 12. It is a region of, for example, about φ2 mm, which includes an intersection where That is, the detection region DA is a spatial region in which the spatial region in which the light of the projection system 11 is projected and the spatial region for guiding the scattered light generated by the light of the projection system 11 hitting the particles 2 to the light receiving system 12 overlap. Is.

The light projecting system 11 includes an optical element that projects light into the detection region DA, and in the present embodiment, the light projecting element 111 and the light projecting arranged in front of the light projecting element 111 (light projecting side). It has a lens 112.

The light projecting element 111 is a solid-state light emitting element such as an LED (Light Emitting Diode) or a semiconductor laser that projects light into the detection region DA. The light projecting element 111 may project light having a predetermined wavelength such as infrared light, blue light, green light, red light, or ultraviolet light, and project a mixed wave having two or more wavelengths. In the present embodiment, in view of the intensity of the light scattered by the particles 2 (scattered light intensity), as the light projecting element 111, for example, a bullet-shaped LED that emits light having a wavelength of 400 nm to 1000 nm is used. ..

The shorter the wavelength of the light projected from the light projecting element 111, the easier it is to detect the particles 2 having a small particle diameter. Further, the light projection control method of the light projecting element 111 is not particularly limited, and the light projected from the light projecting element 111 can be continuous light or pulsed light driven by DC.

The light projecting lens 112 is arranged in front of the light projecting element 111 and on the optical axis P of the light projecting system 11, and is configured to allow the light projected from the light projecting element 111 to travel toward the detection region DA. There is. For example, the light projecting lens 112 is a light condensing lens that collects the light projected from the light projecting element 111 into the detection region DA, and is formed of a transparent resin such as PC (polycarbonate) or glass. That is, the light projected from the light projecting element 111 reaches the detection region DA via the light projecting lens 112. At this time, if the particles 2 are located in the detection region DA, the light from the light projecting element 111 is scattered by the particles 2.

The light receiving system 12 includes an optical element that receives light from the detection region DA, and in the present embodiment, the light receiving system 12 has a light receiving element 121 and a light receiving lens 122 arranged in front of the light receiving element 121 (light incident side). .. When the particles 2 are located in the detection region DA, the light (scattered light) scattered by the particles 2 is received by the light receiving system 12.

The light receiving element 121 receives scattered light from the light projecting element 111 by the particles 2 passing through the detection region DA at a speed dependent on the particle size, and an electric signal including a pulsed waveform corresponding to the particles 2. To generate. That is, the light receiving element 121 generates an electric signal indicating a change in light intensity of the received scattered light over time.

The light receiving element 121 is a photoelectric conversion element that converts the received scattered light into an electric signal, and in the present embodiment, includes at least one of a photodiode and a phototransistor having sensitivity to the light projected by the light projecting element 111. .. That is, the light receiving element 121 outputs an electric signal (here, a current signal) according to the received light intensity. The light receiving element 121 may include, for example, a photo IC diode or a photomultiplier tube.

The light receiving lens 122 is arranged between the detection region DA and the light receiving element 121, and is configured to collect the scattered light by the particles 2 located in the detection region DA on the light receiving element 121. For example, the light receiving lens 122 is a condensing lens that focuses the light scattered by the particles 2 located in the detection region DA on the light receiving element 121, and is made of the same material as the light projecting lens 112.

The housing 13 is a member having a light-shielding property and provided with a particle flow path which is a tubular space region through which ambient air including particles 2 flows. For example, the housing 13 has at least an inner surface black so as to easily attenuate stray light.

The housing 13 is formed by injection molding using, for example, a resin material such as ABS resin. At this time, for example, by forming the housing 13 using a resin material to which a black pigment or dye is added, the inner surface of the housing 13 can be made a black surface to attenuate stray light. Alternatively, by applying a black paint to the inner surface of the housing 13 after injection molding, the inner surface of the housing 13 can be made a black surface to attenuate stray light. Further, the stray light can be attenuated by performing a surface treatment such as embossing on the inner surface of the housing 13.

The housing 13 is provided with an inflow port 18 and an outflow port 19 as described above. Therefore, the ambient air enters the inside of the housing 13 from the inflow port 18, is guided to the detection region DA through the particle flow path, and flows out from the outflow port 19 to the outside of the housing 13.

The heater 15 is a flow velocity generating unit that allows a fluid (here, ambient air) to pass through the detection region DA in a direction that prevents the particles 2 from moving due to their own weight. In the present embodiment, the heater 15 heats the gas around the heater 15 to flow the gas in the particle flow path to generate an air flow. That is, the heater 15 is provided on the lower side in the vertical direction of the detection region DA, and allows the fluid containing the particles to pass vertically upward.

Specifically, when the surrounding gas is heated by the heater 15, the heated gas expands and becomes less dense, so that the heated gas moves upward in the direction opposite to gravity. That is, the heater 15 generates an upward airflow (updraft). When this air flow flows the gas in the particle flow path, an air flow is generated in the particle flow path. As a result, since the ambient air of the particle detection sensor 1 is drawn into the housing 13 from the inflow port 18, more particles 2 can be taken into the sensor unit 10 as compared with the case where the heater 15 is not provided.

[1-2. Signal processing unit]
The signal processing unit 20 calculates the particle size of the particles in the fluid by signal processing the electric signal output from the light receiving element 121. As shown in FIG. 1, the signal processing unit 20 includes an analog signal processing unit 21 that performs analog signal processing and a general-purpose MPU 22 that performs digital signal processing.

The analog signal processing unit 21 is composed of an analog circuit, and in the present embodiment, the current signal output from the light receiving element 121 is subjected to various analog signal processing to output a voltage signal based on the current signal. To do. Here, various analog signal processing includes, for example, I / V conversion for converting current (I) into voltage (V), bandpass filter processing for passing a desired frequency band of an input signal, and input. This is an amplification process that amplifies and outputs the generated signal. The analog signal processing unit 21 includes an IV conversion circuit 211 that performs I / V conversion and an amplifier circuit 212 that performs amplification processing.

The IV conversion circuit 211 generates a voltage signal corresponding to the current signal by performing I / V conversion of the current signal output from the light receiving element 121. By converting the current signal into a voltage signal in this way, the subsequent signal processing can be facilitated, and the design of the amplifier circuit 212 connected to the subsequent stage of the IV conversion circuit 211 can be facilitated.

The amplifier circuit 212 amplifies the voltage signal output from the IV conversion circuit 211 according to a predetermined frequency characteristic. The frequency characteristics of the amplifier circuit 212 will be described later.

The analog signal processing unit 21 configured in this way indicates a detection signal (sensor output) which is an electric signal indicating an output from the light receiving element 121 and including a pulsed waveform corresponding to the particle 2 located in the detection region DA. ) Is output.

The general-purpose MPU 22 is composed of a digital circuit, and detects particles contained in the fluid in the detection region DA by using the detection signal output from the analog signal processing unit 21. As shown in FIG. 1, the general-purpose MPU 22 has an AD conversion unit 221 and a calculation unit 222 as functional blocks.

The AD conversion unit 221 samples (samples) and quantizes the voltage signal amplified by the amplifier circuit 212. In other words, the AD conversion unit 221 generates time-series digital data corresponding to the detection signal by AD (Analog to Digital) conversion of the analog detection signal output from the analog signal processing unit 21. That is, the AD conversion unit 221 generates time-series digital data based on the current signal output from the light receiving element 121.

In the present embodiment, the AD conversion unit 221 is an AD conversion module previously incorporated in the general-purpose MPU 22, and converts a voltage signal input to the analog input terminal of the general-purpose MPU 22 into digital data. For example, the AD conversion unit 221 samples a voltage signal in the range of 0.0 to 5.0 V input to the analog input terminal of the general-purpose MPU 22 at a predetermined sampling cycle. After that, the AD conversion unit 221 generates the above-mentioned time-series digital data by converting the voltage of the sampled voltage signal into a 10-bit digital value.

The calculation unit 222 calculates the particle size and the number of particles contained in the fluid in the detection region DA by using the digital data generated by the AD conversion unit 221. Specifically, the calculation unit 222 calculates the particle size of the particles contained in the fluid in the detection region DA by using the pulse width of the pulse data included in the digital data. Here, the pulse data is time-series digital data corresponding to the pulse-shaped waveform included in the detection signal. That is, the calculation unit 222 calculates the particle diameter of the particles that have passed through the detection region DA based on the pulse width of the pulsed waveform included in the electric signal after amplification by the amplifier circuit 212.

For example, the calculation unit 222 calculates the particle diameter based on the pulse width at a predetermined threshold value. Further, the calculation unit 222 further counts the number of particles that have passed through the detection region DA within the predetermined period by counting the number of peaks that exceed the threshold value in the predetermined period (for example, 1 minute).

The details of the mechanism for calculating the particle diameter by the particle detection sensor 1 will be described later.

Such a general-purpose MPU 22 is realized by, for example, a system LSI which is an integrated circuit, and may be individually integrated into one chip for each functional block, or may be integrated into one chip so as to include a part or all of them. Further, the general-purpose MPU 22 is not limited to the system LSI, and may be realized by a dedicated circuit or a general-purpose processor. Further, the general-purpose MPU 22 may use an FPGA (Field Programmable Gate Array) that can be programmed after the LSI is manufactured, or a reconfigurable processor that can reconfigure the connection and settings of the circuit cells inside the LSI.

[2. Particle size calculation mechanism]
Next, the mechanism for calculating the particle diameter by the particle detection sensor 1 configured as described above will be described.

FIG. 2 is a diagram schematically showing the state of the particles 2 in the fluid passing through the detection region DA. In the figure, the fluid passing through the detection region DA (updraft by the heater 15 in the present embodiment) is also schematically shown by a thick arrow. Further, in the figure, the drag force acting on the particles 2 in the fluid due to gravity is also schematically shown, and the larger the drag force, the longer the arrow.

As shown in the figure, particles 2 having various sizes are conveyed to the detection region DA by the updraft from the heater 15. At this time, the particles pass through the detection region DA at a speed that depends on the particle size. Specifically, the velocity of fine particles having a small particle diameter (for example, particles having a particle diameter of 0.3 μm) is higher than that of coarse particles having a large particle diameter (for example, particles having a particle diameter of 30 μm). .. This is due to the difference in the weight of the particles due to the difference in particle diameter, that is, the difference in the drag due to the weight against the updraft.

Therefore, the time required for passing through the detection region DA becomes longer for particles having a larger particle size and shorter for particles having a smaller particle size. Further, the light intensity of the scattered light by the particles located in the detection region DA increases as the particle size increases, and decreases as the particle size decreases. Therefore, the light intensity of the scattered light changes in a pulsed manner with time according to the particle size.

As a result, the electric signal input from the light receiving element 121 to the amplifier circuit 212 includes the following pulse-shaped waveform. That is, the electric signal includes a pulse-like waveform in which both the pulse width and the crest value are large when the particles having a large particle diameter pass through the detection region DA. That is, at this time, the frequency of the electric signal input to the amplifier circuit 212 becomes low. On the other hand, the electric signal includes a pulse-like waveform in which both the pulse width and the crest value are small when the particles having a small particle diameter pass through the detection region DA. That is, at this time, the frequency of the electric signal input to the amplifier circuit 212 becomes high.

Here, the amplifier circuit 212 amplifies the electric signal with a larger amplification factor as the frequency of the electric signal input from the light receiving element 121 is higher. Specifically, in the present embodiment, the amplifier circuit 212 amplifies so that the peak value of the pulsed waveform included in the amplified electric signal is within a predetermined range.

For example, the amplifier circuit 212 has the frequency characteristics as shown in FIG. FIG. 3 is a graph showing an outline of the frequency characteristics of the amplification factor (amplification circuit gain) of the amplifier circuit 212.

Due to such frequency characteristics, the amplifier circuit 212 amplifies an electric signal including a pulsed waveform of frequency fa caused by particles having a particle diameter of 30 μm passing through the detection region DA at an amplification factor Ga. Further, the amplifier circuit 212 transmits an electric signal including a pulsed waveform having a frequency fb (however, fa <fb) due to the passage of particles having a particle diameter of 0.3 μm through the detection region DA with an amplification factor Gb (however, Ga <. Amplify with Gb).

Therefore, the electric signal after amplification by the amplifier circuit 212 includes one or more pulse-shaped waveforms whose peak value is within a predetermined range.

The amplifier circuit 212 may amplify the electric signal at a higher amplification factor as the frequency of the input electric signal is higher, at least within a predetermined frequency range. That is, the time required for a particle to pass through the detection region DA has two factors: (i) the size of the detection region DA (optical focal area diameter) and (ii) the moving speed of the particle passing through the detection region DA. Determined by. For example, the size of the detection region DA is rd [mm], the movement speed of the minimum particles that can pass through the detection region DA is v1 [mm / sec], and the movement speed of the maximum particles that can pass through the detection region DA is v2. When [mm / sec] is set, the predetermined frequency range fw [Hz] is v2 / rd ≦ fw ≦ v1 / rd. Here, the moving speed of the particles passing through the detection region DA (ii) depends on the particle diameter, and is obtained from the flow velocity of the fluid passing through the detection region DA, the drag force of the particles against the fluid, and the like.

FIG. 4 is a diagram conceptually showing the amplification process by the amplifier circuit 212. Specifically, (a) of the figure is a graph showing the intensity of scattered light by particles that have passed through the detection region DA in chronological order. (B) in the figure is an amplified electrical signal (particle detection signal) corresponding to the scattered light shown in (a) in the figure.

As shown in FIG. 4A, the peak of the scattered light intensity by the particles increases as the particle size increases. For example, when the particle size is 30 μm, the peak is compared with the case where the particle size is 0.3 μm. , Reach tens of thousands of times. Therefore, the electric signal input from the light receiving element 121 having a substantially constant photoelectric conversion efficiency to the amplifier circuit 212 is accompanied by a difference in peak value equivalent to such an intensity ratio. Here, substantially constant means not only completely constant, but also substantially constant. That is, "omitted" includes an error of about several percent.

The amplifier circuit 212 amplifies such an electric signal at an amplification factor having the frequency characteristics shown in FIG. 3, so that the peak value as shown in FIG. 4B is within a predetermined range. Convert to an electrical signal.

As a result, the peak value of the pulsed waveform (that is, the height of the electrical signal after amplification) is kept within a predetermined range for both coarse particles having a particle diameter of 30 μm and fine particles having a particle diameter of 0.3 μm. Can be adjusted.

Here, the predetermined range is determined by, for example, the maximum input voltage of the general-purpose MPU 22 in the subsequent stage, the saturation voltage of the analog element (not shown) constituting the analog signal processing unit 21 in the subsequent stage from the amplifier circuit 212, or the like. , The range is below the saturation level Vmax.

As shown in FIG. 4B, the one or more pulse-shaped waveforms included in the amplified electric signal are waveforms in which the peak value is within a predetermined range and the pulse width depends on the particle size. Therefore, the calculation unit 222 calculates the particle size of the particles that have passed through the detection region DA based on the pulse width of the pulsed waveform included in the amplified electric signal.

Specifically, the calculation unit 222 acquires the pulse width at the threshold value Vth for each pulse-shaped waveform. For example, the calculation unit 222 compares the amplified electric signal with the threshold value Vth using a counter (not shown) and a comparator (not shown) of the general-purpose MPU 22, and the time when the amplified electric signal becomes the threshold value Vth or more. The pulse width at the threshold value Vth is extracted by measuring.

Next, the calculation unit 222 calculates the particle diameter of the particles that have passed through the detection region DA from the extracted pulse width, for example, with reference to the predetermined pulse width correlation information indicating the correlation between the pulse width and the particle diameter. .. Here, the pulse width correlation information indicates the correlation between the pulse width and the particle size, and is stored in the memory (not shown) of the general-purpose MPU 22 or incorporated as a code executed by the general-purpose MPU 22. There is.

As a result, the calculation unit 222 sets the particle diameter of the particles that have passed through the detection region DA to 0.3 μm for each of the pulse waveforms whose extracted pulse widths are T11, T12, and T13 (however, T11 <T12 <T13). , 2.5 μm, and 30 μm.

[3. Summary]
As described above, the particle detection sensor 1 according to the present embodiment is projected by a light projecting element 111 that projects light onto the detection region DA and particles 2 that pass through the detection region DA at a speed that depends on the particle size. It includes a light receiving element 121 that receives scattered light from the light element 111 and generates an electric signal including a pulsed waveform corresponding to the particle 2. Further, the particle detection sensor 1 includes an amplifier circuit 212 that amplifies the electric signal with a larger amplification factor as the frequency of the electric signal input from the light receiving element 121 is higher. Further, the particle detection sensor 1 includes a calculation unit 222 that calculates the particle diameter of the particles 2 that have passed through the detection region DA based on the pulse width of the pulsed waveform included in the amplified electric signal.

As described above, the higher the frequency of the input electric signal by the amplifier circuit 212, the larger the amplification factor, so that the saturation of the electric signal after amplification can be suppressed. That is, it is not necessary to increase the dynamic range of the circuit that processes the electric signal (the signal processing unit 20 in the present embodiment). Further, the calculation unit 222 can calculate a wide particle diameter from fine particles to coarse particles by calculating the particle diameter based on the pulse width of the pulsed waveform included in the amplified electric signal. Therefore, it is possible to widen the dynamic range of the particle size that can be determined without increasing the dynamic range of the circuit that processes the electric signal.

Further, the particle detection sensor 1 according to the present embodiment is a flow velocity generating unit (heater 15 in the present embodiment) that allows the fluid containing the particles to pass through the detection region DA in a direction that hinders the movement of the particles 2 due to their own weight. To be equipped.

As a result, for example, the amount (number) of particles passing through the detection region DA can be adjusted.

Further, according to the present embodiment, the flow velocity generating portion allows the fluid to pass vertically upward.

As a result, the time required for passing through the particle detection region DA can be greatly varied depending on the particle diameter. Therefore, the pulse width of the pulse waveform included in the amplified electric signal changes greatly depending on the particle size. Therefore, the accuracy of calculating the particle size based on the pulse width can be improved.

Further, according to the present embodiment, the flow velocity generating portion is a heater 15 provided on the lower side in the vertical direction of the detection region DA.

As a result, the configuration of the flow velocity generating portion can be simplified.

(Modification example 1)
In addition, in order to improve the calculation accuracy of the particle size, the calculation unit 222 may further calculate the particle size by using the crest value. Therefore, a particle detection sensor including such a calculation unit 222 will be described below as a modification 1 of the embodiment. The particle detection sensor according to the present modification is mainly different in the process of calculating the particle diameter by the calculation unit 222 as compared with the embodiment, and the other configurations or processes are the same. Therefore, in the following, the same configuration or processing as in the embodiment will be described in a simplified or omitted manner. Further, also in the following modification examples, the configurations or processes already described will be described in a simplified or omitted manner.

In this modification, the calculation unit 222 calculates the particle size of the particles that have passed through the detection region DA based on the peak value of the pulsed waveform included in the amplified electric signal. For example, the calculation unit 222 extracts the peak value of the pulsed waveform by extracting the value at the time of peak hold or when the rate of increase of the electric signal changes from plus to minus.

Next, the calculation unit 222 calculates the particle diameter of the particles that have passed through the detection region DA from the extracted crest value, for example, with reference to the predetermined crest value correlation information indicating the correlation between the crest value and the particle diameter. .. Here, the crest value correlation information shows the correlation between the crest value and the particle size, and is stored in the memory (not shown) of the general-purpose MPU 22 or by the general-purpose MPU 22 as well as the pulse width correlation information, for example. Built in as code to be executed.

As a result, the calculation unit 222 calculates the particle diameter of the particles that have passed through the detection region DA for each of the extracted peak values.

Next, the calculation unit 222 combines the particle diameter calculated using the pulse width (hereinafter, first particle diameter) and the particle diameter calculated using the peak value (hereinafter, second particle diameter) in the detection region. The particle size of the particles that have passed through DA is calculated. For example, the calculation unit 222 sets the particle diameter of the particles that have passed the detection region DA to any value (mean value, median value, etc.) within the particle diameter range defined by the first particle diameter and the second particle diameter. Calculate as.

As described above, according to the present modification, the calculation unit 222 further calculates the particle size of the particles that have passed through the detection region DA based on the peak value of the pulsed waveform included in the amplified electric signal. ..

In this way, the calculation unit 222 calculates the particle diameter based on the pulse width and the crest value, so that the calculation accuracy of the particle diameter can be improved.

Further, by calculating the particle diameter based not only on the pulse width but also on the peak value, for example, due to restrictions on the characteristics of the analog element (not shown) constituting the analog signal processing unit 21, the electric signal after amplification can be obtained. Even when the peak values of a plurality of included pulse-shaped waveforms cannot be equalized, it is possible to reduce the calculation error of the particle size.

Specifically, when the peak values of a plurality of pulse-shaped waveforms are different from each other, the extracted pulse width and the particle size of the particles that have passed through the detection region DA are different from the correlation indicated by the pulse width correlation information. In some cases. In this case, an error may occur in the calculation result of the particle size using only the extracted pulse width. On the other hand, by calculating the particle diameter based not only on the pulse width but also on the crest value, it is possible to reduce the calculation error of the particle diameter as compared with the calculation result of the particle diameter using only the pulse width.

(Modification 2)
In the above-described embodiment and the first modification thereof, the description has been made on the assumption that only one particle passes through the detection region DA, but a plurality of particles may pass through the detection region DA. Therefore, as a second modification of the embodiment, a particle detection sensor capable of calculating the particle diameter of each particle even when a plurality of particles pass through the detection region DA at the same time will be described below. Here, passing through the detection area DA at the same time means that the time from the first time to the last time of passing through the detection area DA is not limited to the same, and the two are located together in the detection area DA at any time. ..

FIG. 5 is a graph showing an electric signal after amplification by the amplifier circuit 212 in this modification.

The waveform W20 shown in the figure is a pulse-shaped waveform obtained by simultaneously passing a particle having a particle diameter of 30 μm and a particle having a particle diameter of 2.5 μm through the detection region DA. Specifically, the waveform W20 is a composite waveform of a waveform W21 corresponding to a particle having a particle diameter of 30 μm and a waveform W22 corresponding to a particle having a particle diameter of 2.5 μm.

Such a waveform W20 will have a plurality of peaks unless the peak of the waveform W21 and the peak of the waveform W22 have the same timing. That is, the waveform W20 takes a plurality of peak values.

Therefore, in this modification, the calculation unit 222 sets the detection region DA based on each of the m pulse widths at the same threshold value for one pulse-shaped waveform in which the number of crest values is 2 or more and m. The particle size of each of the m particles that have passed is calculated.

Specifically, in this modification, the calculation unit 222 acquires the number of peak values for each pulse-shaped waveform included in the amplified electric signal. Next, for the pulsed waveform (waveform W20 in FIG. 5) in which the number of peak values is 2 or more, it is determined that a plurality of particles have passed through the detection region DA at the same time, and the same threshold value (threshold value in FIG. 5) is determined. The particle diameter is calculated based on each of the pulse widths (pulse widths T21 and T22 in FIG. 5) in Vth2). That is, the particle diameter is calculated based on the pulse width at the threshold value at which the same number of pulse widths as the number of peak values can be extracted.

For example, the calculation unit 222 calculates two particle diameters of the waveform W20 based on the pulse widths T21 and T22 at the threshold value (here, the threshold value Vth2) at which two pulse widths can be extracted. As a result, the calculation unit 222 calculates that the particle diameter of the particles that have passed through the detection region DA is 30 μm for the waveform W21 whose extracted pulse width is T21 in the waveform W20. Further, the calculation unit 222 calculates that the particle diameter of the particles that have passed through the detection region DA is 2.5 μm for the waveform W22 in which the extracted pulse width is T22 in the waveform W20.

Here, as shown in FIG. 5, a plurality of threshold values (four in this case) may be set, and the pulse width correlation information may correspond to each of the plurality of threshold values. That is, the calculation unit 222 refers to the pulse width correlation information corresponding to the smallest threshold value (threshold value Vth4 in FIG. 5) among the plurality of threshold values for the pulse-shaped waveform in which the number of crest values is only one. , The particle size may be calculated based on the extracted pulse width.

As described above, according to this modification, the calculation unit 222 has m pulses at the same threshold value for a pulse-shaped waveform (waveform W20 in FIG. 5) in which the number of crest values is 2 or more and m. Based on each of the widths (two pulse widths T21 and T22 at the threshold value Vth2 in FIG. 5), the particle diameter of each of the m particles (two in FIG. 5) that have passed through the detection region DA is calculated.

Thereby, it is possible to calculate the particle diameter of each of the plurality of particles that simultaneously pass through the detection region DA while widening the dynamic range of the particle diameter that can be determined.

In this modification, the case where two particles pass through the detection region DA at the same time has been described, but even when three or more particles pass through the detection region DA at the same time, the same processing is performed to perform 3 The particle size of each of the two or more particles can be calculated.

(Modification 3)
In the above-described embodiment and the modifications 1 and 2 thereof, the amplifier circuit 212 amplifies the peak value of the pulsed waveform included in the amplified electric signal within a predetermined range. However, the amplification factor of the amplifier circuit 212 is not limited to this. Therefore, the particle detection sensor according to the third modification of the embodiment will be described below.

In this modification, the amplifier circuit 212 amplifies so that the larger the particle size of the particles, the smaller the peak value of the pulsed waveform included in the amplified electric signal. That is, the amplifier circuit 212 has a frequency characteristic in which the change (that is, the slope) of the amplification factor with respect to the frequency is larger than the frequency characteristic shown in FIG.

As a result, the amplified electrical signal becomes, for example, a signal as shown in FIG. FIG. 6 is a graph showing an electric signal after amplification by the amplifier circuit 212 in this modification.

The waveform W30 shown in the figure is a pulse-shaped waveform obtained by simultaneously passing a particle having a particle diameter of 0.3 μm and a particle having a particle diameter of 30 μm through the detection region DA. Specifically, the waveform W30 is a composite waveform of a waveform W31 corresponding to a particle having a particle diameter of 0.3 μm and a waveform W32 corresponding to a particle having a particle diameter of 30 μm.

In such a waveform W30, the pulse width changes abruptly on the way. Specifically, when one particle passes through the detection region DA, the pulsed waveform changes smoothly, for example, based on the distribution (sensitivity) of the light intensity of the scattered light with respect to the passage position of the particle in the detection region DA. It becomes a predetermined waveform. On the other hand, when a plurality of particles pass through the detection region DA at the same time, the pulsed waveform becomes a waveform that changes rapidly unlike the predetermined waveform.

Therefore, in the present modification, the calculation unit 222 sets the first pulse width at the first threshold value and the second pulse width at the second threshold value smaller than the first threshold value for the pulsed waveform included in the amplified electric signal. If the relative relationship of the above does not satisfy a predetermined relationship, the particle size of each of the two or more particles that have passed through the detection region DA is calculated based on each of the first pulse width and the second pulse width.

Specifically, in this modification, the calculation unit 222 extracts the pulse width at each of a plurality of threshold values (here, four threshold values Vth1 to Vth4) for each pulse-shaped waveform included in the amplified electric signal. To do.

Next, the calculation unit 222 determines whether or not the relative relationship (for example, the ratio of the pulse widths) of the pulse widths at each of the two adjacent thresholds satisfies a predetermined relationship (for example, a predetermined value or less).

Next, when the relative relationship satisfies the predetermined relationship, the calculation unit 222 refers to the pulse width correlation information corresponding to the smallest threshold value (threshold value Vth4 in FIG. 6) among the plurality of threshold values, and extracts the pulse width. The particle size is calculated based on. On the other hand, when the relative relationship does not satisfy the predetermined relationship, the calculation unit 222 calculates the particle size based on the extracted two pulse widths by referring to the pulse width correlation information corresponding to each of the two threshold values. To do.

For example, the calculation unit 222 has a relative relationship (ratio T31 /) between the pulse width T31 (first pulse width) at the threshold value Vth2 (first threshold value) and the pulse width T32 (second pulse width) at the threshold value Vth3 (second threshold value). When T32) does not satisfy a predetermined relationship (predetermined value α or less), the particle size is calculated as follows. Specifically, with reference to the pulse width correlation information corresponding to the threshold value Vth2, the particle diameter of the particles that have passed through the detection region DA is calculated to be 0.3 μm for the waveform W31 in which the extracted pulse width is T31. Further, with reference to the pulse width correlation information corresponding to the threshold value Vth3, the particle diameter of the particles that have passed through the detection region DA is calculated to be 30 μm for the waveform W32 in which the extracted pulse width is T32.

As described above, according to the present modification, the amplifier circuit 212 amplifies so that the larger the particle size of the particles, the smaller the peak value of the pulsed waveform included in the amplified electric signal.

As a result, even when the coarse particles and the fine particles pass through the detection region DA at the same time, the amplified electric signal includes a pulse-shaped waveform corresponding to each of the coarse particles and the fine particles. That is, in the amplified electrical signal, a part of the pulsed waveform corresponding to the fine particles appears without being hidden by the pulsed waveform corresponding to the coarse particles. Therefore, even when the coarse particles and the fine particles pass through the detection region DA at the same time, the particle diameters of the coarse particles and the fine particles can be calculated.

Further, according to this modification, the calculation unit 222 has a pulse-like waveform (waveform W30 in FIG. 6) included in the amplified electric signal at the first pulse width at the first threshold (at the threshold Vth2 in FIG. 6). When the relative relationship between the pulse width T31) and the second pulse width at the second threshold smaller than the first threshold (pulse width T32 at the threshold Vth3 in FIG. 6) does not satisfy a predetermined relationship, the first pulse width and the second Based on each of the pulse widths, the particle size of each of the two or more particles that have passed through the detection region DA is calculated.

Thereby, it is possible to calculate the particle diameter of each of the plurality of particles that simultaneously pass through the detection region DA while widening the dynamic range of the particle diameter that can be determined.

(Modification example 4)
In the above embodiment, the detection region DA has a spatial region in which the light of the light projecting system 11 is projected and a spatial region for guiding the scattered light generated by the light of the light projecting system 11 hitting the particles 2 to the light receiving system 12. It was explained that it is an overlapping spatial area. The shape of the detection region DA is not particularly limited, but is preferably a flat shape from the viewpoint of improving the calculation accuracy of the particle size. Therefore, as the particle detection sensor according to the modified example 4 of the embodiment, a configuration including a flat detection region DA will be described.

FIG. 7 is a diagram schematically showing the state of the particles 2 in the fluid passing through the detection region DA in this modification. In the same figure, similarly to FIG. 2, the fluid passing through the detection region DA and the drag force acting on the particles 2 are also schematically shown.

As shown in the figure, the detection region DA in this modification has a flat shape having a substantially constant thickness in the passing direction when viewed in one direction perpendicular to the passing direction of the particles. In this modification, since the fluid is an updraft due to the heater 15, the detection region DA is viewed in one horizontal direction (here, in the depth direction of the paper surface), and the thickness in the vertical direction is substantially constant. There is. For example, the thickness of the detection region DA in the depth direction of the paper surface gradually increases from the edge portion to the center portion. Further, the shape of the detection region DA viewed in the vertical direction is not particularly limited, and is, for example, a substantially rectangular shape or a substantially circular shape.

Such a detection region DA is realized, for example, by appropriately designing and arranging various optical elements constituting the light projecting system 11 and the light receiving system 12.

Here, when the detection region DA is spherical, even when particles having the same particle diameter pass through the detection region DA, the pulse width of the pulsed waveform depends on the passage position of the particles in the detection region DA. Will be different. Specifically, when the particles pass through the central portion of the spherical detection region DA, the pulse width becomes larger than when the particles pass through the end portion of the detection region DA. This can be a factor that lowers the accuracy of calculating the particle size.

On the other hand, according to the present modification, the detection region DA has a flat shape in which the thickness in the passing direction is substantially constant when viewed in one direction perpendicular to the passing direction of the particles.

As a result, the dependence of the pulse width on the passing position of the particles in the detection region DA can be suppressed, so that the calculation accuracy of the particle diameter can be improved. In particular, when the thickness of the detection region DA is a plate shape that is substantially constant in the direction perpendicular to the passage direction of the fluid, it is possible to increase the decrease in the accuracy of calculating the particle size.

(Modification 5)
In the above embodiment, the particle detection sensor 1 includes a heater 15 as a flow velocity generating unit for generating a fluid flow in the detection region DA. However, the particle detection sensor does not have to be provided with a flow velocity generating portion such as a heater 15, and a fluid flow (air flow) is generated in the detection region DA by a flow velocity generating portion such as a fan (small fan) provided outside. It doesn't matter. Therefore, the particle detection sensor configured in this way will be described below as a modification 5 of the embodiment.

FIG. 8 is a block diagram showing an example of the configuration of the particle detection sensor 1A according to the modified example 5 of the embodiment.

As shown in the figure, in the particle detection sensor 1A according to the present modification, an air flow is generated in the detection region DA by the external fan 15A without the heater 15 as compared with the particle detection sensor 1 according to the embodiment. To do.

The fan 15A is a flow velocity generating unit that allows the fluid to pass through the detection region DA in a direction that hinders the movement of the particles due to their own weight. For example, an air conditioner (for example, an air purifier or an air conditioner) on which the particle detection sensor 1A is mounted. Etc.). The airflow generated by the fan 15A is branched into a mainstream, which is an airflow for the air conditioner to perform air conditioning, and a tributary introduced into the particle detection sensor 1A. The air flow introduced into the particle detection sensor 1A in this way generates a gas flow in the detection region DA.

Even with the particle detection sensor 1A configured in this way, it is possible to make a determination without increasing the dynamic range of the circuit that processes the electric signal (signal processing unit 20 in this modification), as in the above embodiment. The dynamic range of various particle sizes can be widened (wide dynamic range).

(Modification 6)
The particle detection sensors described in the above embodiments and modifications 1 to 5 can be applied to various devices such as air conditioners such as air purifiers and air conditioners, dust sensors and smoke detectors. Therefore, an application example of the particle detection sensor will be described below as a modification 6 of the embodiment.

FIG. 9 is an external view of an air purifier including a particle detection sensor. FIG. 10 is an external view of a smoke detector including a particle detection sensor. FIG. 11 is an external view of a ventilation fan including a particle detection sensor. FIG. 12 is an external view of an air conditioner including a particle detection sensor.

According to these devices, by providing a particle detection sensor having a wide dynamic range of the particle diameter range that can be determined, the operation can be switched according to the detection result of, for example, fine particles and coarse particles.

(Other variants)
Although the present invention has been described above based on the embodiments and modifications, the present invention is not limited to the above embodiments and modifications.

For example, in the above description, the amplifier circuit 212 amplifies the electric signal with a larger amplification factor as the frequency of the input electric signal is higher. However, in the present invention, if at least one of the amplification factor (amplifier circuit gain) of the amplifier circuit 212 and the conversion efficiency (light receiving element gain) of the light receiving element 121 has a frequency characteristic that the gain increases as the frequency increases. Good. That is, the particle detection sensor may include the following light receiving element and amplifier circuit instead of the light receiving element 121 and amplifier circuit 212 described above.

Specifically, the light receiving element receives the scattered light of the light from the light projecting element 111 by the particles passing through the detection region DA at a speed depending on the particle size. Then, the light receiving element performs photoelectric conversion with a higher conversion efficiency as the frequency obtained by the temporal change of the received scattered light increases, and generates an electric signal including a pulsed waveform corresponding to the particles. Further, the amplifier circuit amplifies the electric signal input from the light receiving element at, for example, a substantially constant amplification factor.

Here, the temporal change of the scattered light is due to the particles passing through the detection region DA. Therefore, the frequency obtained by the temporal change of the scattered light depends on the velocity of the particles passing through the detection region DA, and the higher the velocity of the particles, the higher the frequency.

Even with the particle detection sensor configured in this way, as in the particle detection sensor 1 according to the above embodiment, a pulse-like waveform having a pulse width corresponding to the particle size while suppressing saturation of the peak value. Will be included. Therefore, as in the above embodiment, the dynamic range of the particle diameter that can be determined can be widened without increasing the dynamic range of the circuit that processes the electric signal.

Further, the calculation unit 222 may calculate the particle diameter, and may not calculate the number of particles.

Further, the flow velocity generating unit is not limited to the vertically upward direction, and the fluid may pass through the detection region DA in a direction that hinders the movement of the particles 2 due to their own weight. That is, the flow velocity generating unit may generate a force that opposes gravity, and may allow the fluid to pass upward from the horizontal direction.

Further, for example, the general-purpose MPU 22 may adjust the flow velocity of the fluid passing through the detection region DA by controlling the flow velocity control unit. Thereby, for example, the flow velocity can be appropriately adjusted according to the particle size range of the detection target so that the peak value of the pulse waveform included in the amplified electric signal becomes a desired value. Therefore, it is expected that the calculation accuracy of the particle size will be improved.

Further, in the above description, the medium containing the particles is a gas (air), but a medium other than a gas (a liquid such as water) may be used. That is, the particle detection sensor detects particles contained in a fluid that is a gas or a liquid.

Further, in the above description, each component in the general-purpose MPU 22 may be configured by dedicated hardware or may be realized by executing a software program suitable for each component. Each component may be realized by a program execution unit such as a CPU or a processor reading and executing a software program recorded on a recording medium such as a hard disk or a semiconductor memory.

In addition, some or all of the constituent elements (functions) constituting the general-purpose MPU 22 are realized as a part of a microprocessor, ROM, RAM, etc. mounted on various devices (for example, an air purifier) equipped with a particle detection sensor. It doesn't matter if you have it.

Further, the present invention can be realized not only as such a particle detection sensor but also as a method including a step (process) performed by the particle detection sensor.

For example, those steps may be performed by a computer (computer system). Then, the present invention can be realized as a program for causing a computer to execute the steps included in those methods. Further, the present invention can be realized as a non-temporary computer-readable recording medium such as a CD-ROM on which the program is recorded.

For example, when the present invention is realized by a program (software), each step is executed by executing the program using hardware resources such as a computer CPU, memory, and input / output circuits. That is, each step is executed by the CPU acquiring data from the memory or the input / output circuit or the like and performing an operation, or outputting the operation result to the memory or the input / output circuit or the like.

In addition, it is realized by applying various modifications to each embodiment that can be conceived by those skilled in the art, or by arbitrarily combining the components and functions of each embodiment within the range not deviating from the gist of the present invention. The form is also included in the present invention.

1, 1A particle detection sensor 2 particles 15 heater (flow velocity generator)
15A fan (flow velocity generator)
20 Signal processing unit 111 Floodlight element 121 Light receiving element 212 Amplifier circuit 222 Calculation unit

Claims (14)

A light projecting element that projects light into the detection area,
A light receiving element that receives scattered light from the light projecting element by particles passing through the detection region at a speed dependent on the particle size and generates an electric signal including a pulsed waveform corresponding to the particles.
An amplifier circuit that amplifies the electric signal with a larger amplification factor as the frequency of the electric signal input from the light receiving element is higher.
A particle detection sensor including a calculation unit that calculates the particle size of particles that have passed through the detection region based on the pulse width of the pulsed waveform included in the amplified electric signal. A light projecting element that projects light into the detection area,
The scattered light of the light from the light projecting element by the particles passing through the detection region at a speed dependent on the particle size is received, and the higher the frequency obtained by the temporal change of the received scattered light, the higher the conversion efficiency. A light receiving element that is converted to generate an electrical signal containing a pulsed waveform corresponding to the particle.
An amplifier circuit that amplifies the electrical signal input from the light receiving element, and
A particle detection sensor including a calculation unit that calculates the particle size of particles that have passed through the detection region based on the pulse width of the pulsed waveform included in the amplified electric signal. The particle detection sensor according to claim 1 or 2, wherein the calculation unit further calculates the particle size of the particles that have passed through the detection region based on the peak value of the pulsed waveform included in the amplified electric signal. The particle detection sensor according to any one of claims 1 to 3, wherein the amplifier circuit amplifies the peak value of the pulsed waveform included in the amplified electric signal so as to be within a predetermined range. The calculation unit is based on each of the m pulse widths at the same threshold value for the pulsed waveform in which the number of peak values of the pulsed waveform included in the amplified electric signal is 2 or more and m. The particle detection sensor according to any one of claims 1 to 4, which calculates the particle size of each of the m particles that have passed through the detection region. The particle detection sensor according to any one of claims 1 to 3, wherein the amplifier circuit amplifies so that the larger the particle size of the particles, the smaller the peak value of the pulsed waveform included in the amplified electric signal. .. The calculation unit has a predetermined relationship between the first pulse width at the first threshold and the second pulse width at the second threshold smaller than the first threshold for the pulsed waveform included in the amplified electric signal. The particle detection sensor according to claim 6, wherein the particle size of each of the two or more particles that have passed through the detection region is calculated based on each of the first pulse width and the second pulse width. The particle detection sensor according to any one of claims 1 to 7, wherein the detection region has a flat shape having a substantially constant thickness in the passing direction when viewed in one direction perpendicular to the passing direction of the particles. The particle detection sensor according to any one of claims 1 to 8, further comprising a flow velocity generating unit that allows a fluid containing the particles to pass through the detection region in a direction that prevents the particles from moving due to their own weight. The particle detection sensor according to claim 9, wherein the flow velocity generating unit allows the fluid to pass vertically upward. The particle detection sensor according to claim 10, wherein the flow velocity generating unit is a heater provided on the lower side in the vertical direction of the detection region. A dust sensor comprising the particle detection sensor according to any one of claims 1 to 11. A smoke detector comprising the particle detection sensor according to any one of claims 1 to 11. The particle detection sensor according to any one of claims 1 to 8.
An air conditioner including a flow velocity generating unit that allows a fluid containing the particles to pass through the detection region in a direction that prevents the particles from moving due to their own weight.

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