JP4950842B2 - Airborne particle measurement system - Google Patents

Description

  The present invention relates to a suspended particle measurement system that measures the type and concentration of suspended particles present in a monitoring space.

  Conventionally, suspended particles (smoke particles, dust, etc.) that exist in the monitoring space are used for the purpose of determining the presence or absence of a fire by measuring the smoke concentration, for example, and managing the state of the clean room used in the semiconductor manufacturing process. Suspended particle measuring systems that measure the type and concentration of steam, steam, etc.) have been proposed.

  As this kind of suspended particle measurement system, a system that measures the type (size) and concentration (number) of suspended particles using scattered light of suspended particles of laser light is known (for example, Patent Document 1, Patent). Reference 2). Here, the suspended particle measuring system described in Patent Document 1 irradiates the suspended particles with one of the laser beams divided into two by a demultiplexer to generate scattered light, and frequency shifts the other laser beam. Then, the size and number of suspended particles are measured using an optical heterodyne method in which the synthesized light is combined with the scattered light, and the combined light is received by a photodetector to detect and process a beat signal. On the other hand, the suspended particle measuring system described in Patent Document 2 scans laser light emitted from a laser oscillator with a polygon mirror having a plurality of mirror surfaces, and has a rectangular opening for scattered light from the suspended particles of the scanned light. It is detected by a CCD camera through a mask, and the amount of suspended particles is measured based on the detected scattered light.

By the way, as described above, the suspended particle measurement system using the scattered light by the suspended particles of the laser beam scans the demultiplexer for dividing the laser beam and the laser beam in addition to the laser light source and the photodetector (or CCD camera). There is a problem that an optical member such as a polygon mirror is required, and the system is large, large, and expensive.
JP-A 63-63944 Japanese Patent Laid-Open No. 7-229826

  In order to solve the problems of the suspended particle measurement system using scattered light, the applicant of the present application has proposed a suspended particle measurement system that measures the concentration of suspended particles using sound waves (for example, ultrasonic waves).

  As shown in FIG. 15, the suspended particle measurement system includes a sound source unit 1 capable of transmitting ultrasonic waves, a control unit 2 that controls the sound source unit 1, and a sound pressure of ultrasonic waves transmitted from the sound source unit 1. And a signal processing unit 4 that measures the concentration of suspended particles existing in the monitoring space between the sound source unit 1 and the wave receiving element 3 based on the output of the wave receiving element 3. The signal processing unit 4 includes concentration estimation means 42 that estimates the concentration of suspended particles in the monitoring space based on the attenuation amount from the reference value of the output of the wave receiving element 3. That is, when particles enter the monitoring space, the sound pressure of the ultrasonic waves from the sound source unit 1 decreases before reaching the wave receiving element 3, and the attenuation of the output of the wave receiving element 3 becomes the concentration of suspended particles in the monitoring space. Since it increases approximately proportionally, the concentration of suspended particles can be estimated based on this attenuation.

By the way, the applicant of the present application determines the output frequency of the sound source unit 1 and the unit attenuation rate of the sound pressure as shown in FIG. 16 according to the type of suspended particles in the monitoring space between the sound source unit 1 and the wave receiving element 3. I got the knowledge that the relationship is different. Here, the sound pressure (hereinafter referred to as a reference sound pressure) received by the wave receiving element 3 in the absence of suspended particles in the monitoring space is defined as I ₀ , a dimming smoke densitometer (darkening smoke detector) the sound pressure of airborne particles of the concentration to be x [% / m] is reception at wave receiving element 3 in the state they exist in the monitoring space when the I _x evaluation at), (I ₀ -I _The value represented by _{x 1} ) / I ₀ is defined as the sound pressure attenuation rate, and in particular, the attenuation rate when x = 1 is defined as the unit attenuation rate. Here, it is assumed that the reference sound pressure I ₀ and the sound pressure I _x are detected under the same conditions except for the presence or absence of suspended particles in the monitoring space. “A” in FIG. 16 is an approximate curve showing the relationship between the output frequency and unit attenuation rate of sound pressure when the suspended particles are black smoke particles (black circles are measured data), and “B” is the suspended particles. Approximate curve showing the relationship between the output frequency of white smoke particles and the unit attenuation rate of sound pressure (black square is measured data), “C” is the output frequency when the floating particles are steam particles It is an approximate curve (black triangle is measurement data) showing the relationship with the unit attenuation rate of sound pressure, and the unit attenuation rate shown here is when the distance between the sound source unit 1 and the receiving element 3 is set to 30 cm. The data for each output frequency. Further, each data at the right end in FIG. 16 is data when the output frequency is 82 kHz, and FIG. 17 shows the result of normalizing the unit attenuation rate of each output frequency with the data when the output frequency is 82 kHz as 1. . In short, in FIG. 17, the horizontal axis represents the output frequency, and the vertical axis represents the relative unit attenuation rate. The size of white smoke particles is about 800 nm, the size of black smoke particles is about 200 nm, and the size of steam particles is about several μm to 20 μm.

  Based on the above-described knowledge, the applicant of the present application causes a plurality of types of ultrasonic waves having different frequencies to be transmitted from the sound source unit 1, and sends at least a reference value (reference value) of the output of the receiving element 3 to the signal processing unit 4. The output of the wave receiving element 3 with respect to the sound pressure), the relationship between the output frequency of the sound source unit 1 and the relative unit attenuation rate of the output of the wave receiving element 3 according to the type of suspended particles present in the monitoring space and the suspended particle concentration Storage means 44 storing data (data extracted from the above-described FIG. 17), unit attenuation rate (data extracted from the above-described FIG. 16) at a specific frequency (for example, 82 kHz) for each suspended particle, and the sound source unit 1 Particle type estimation that estimates the type of particles floating in the monitoring space using the output of the receiving element 3 for each ultrasonic wave transmitted from the frequency and the relational data stored in the storage means 44 Means 41 and In addition, it is proposed to cause the concentration estimating means 42 to estimate the concentration of suspended particles in the monitoring space based on the attenuation amount from the reference value of the output of the wave receiving element 3 with respect to the ultrasonic wave of a specific frequency (for example, 82 kHz). ing.

  In this ultrasonic suspended particle measuring system, the optical member necessary for the suspended particle measuring system using scattered light is unnecessary, so that the system can be simplified and can be made small and inexpensive.

  However, in order to be able to estimate the type of suspended particles as described above, it is necessary to transmit a plurality of types of ultrasonic waves having different frequencies from the sound source unit 1, which causes the following problems. That is, in order to transmit a plurality of types of ultrasonic waves from the sound source unit 1, a plurality of sound source units 1 that transmit various types of ultrasonic waves are used, or a plurality of types of sound sources 1 can be transmitted from a single sound source unit 1 by a control unit. It is necessary to transmit ultrasonic waves sequentially. In the former case, there is a problem that the cost required for the sound source unit 1 is higher than that in the configuration in which one sound source unit 1 is provided, and the suspended particle measurement system is increased in size. On the other hand, in the latter case, it is necessary to drive the sound source unit 1 at a different driving frequency each time an ultrasonic wave is transmitted from the sound source unit 1, so that compared with a case where one type of ultrasonic wave is transmitted from the sound source unit 1. There is a problem in that the configuration of the control unit is complicated, leading to high costs. In any case, since multiple types of ultrasonic waves are individually transmitted, the estimation accuracy of the type and concentration of suspended particles is low due to variations in the transmitted sound pressure during the transmission of individual ultrasonic waves. Furthermore, since it is necessary to transmit the ultrasonic wave a plurality of times, the power consumption accompanying the transmission of the ultrasonic wave increases.

  The present invention has been made in view of the above reasons, and in a configuration for measuring the type and concentration of suspended particles based on the attenuation amount of ultrasonic waves in a monitoring space, a plurality of types of sound waves are transmitted from a sound source unit. An object of the present invention is to provide a suspended particle measurement system that is not necessary.

  In the invention of claim 1, a sound source unit that transmits a sound wave including a plurality of frequency components, a control unit that controls the sound source unit, a wave receiving element that detects the sound pressure of the sound wave transmitted from the sound source unit, A signal processing unit for measuring the type and concentration of suspended particles existing in the monitoring space between the sound source unit and the receiving element based on the output of the receiving element, and the signal processing unit is detected by the receiving element Frequency component extraction means for extracting the intensity of each frequency component from the collected sound wave, and a reference for the frequency and intensity of each frequency component according to the type and concentration of suspended particles existing in the monitoring space between the sound source unit and the receiving element Floating in the monitoring space using the storage means storing the relationship data with the attenuation amount from the value, the intensity of each frequency component extracted by the frequency component extraction means, and the relationship data stored in the storage means A particle type estimating means for estimating a particle type; And having a concentration estimation means for estimating the concentration of suspended particles in the monitoring space on the basis of the attenuation amount from the reference value of the intensity of a specific frequency component.

  According to this configuration, the signal processing unit has the frequency component extraction unit that extracts the intensity of each frequency component from the sound wave detected by the receiving element, and is extracted by the frequency component extraction unit in the particle type estimation unit. Since the type of particles floating in the monitoring space is estimated using the intensity of each frequency component and the relational data stored in the storage means, the type of particles floating in the monitoring space can be estimated There is no need to transmit a plurality of types of sound waves from the sound source unit. That is, it is only necessary that one type of sound wave including a plurality of frequency components is transmitted from the sound source unit, and the cost required for the sound source unit and the control unit is lower than when a plurality of types of sound waves are transmitted from the sound source unit. If the intensity of a plurality of frequency components is extracted from the sound wave transmitted at once from the sound source unit, the transmission sound pressure varies when each sound wave is transmitted. It is possible to avoid the estimation accuracy of the type and concentration of particles from being lowered and the power consumption accompanying the transmission of sound waves from being increased.

  According to a second aspect of the present invention, in the first aspect of the present invention, the storage means includes, as the relational data, relation data between the frequency of each frequency component and an attenuation rate obtained by dividing the attenuation from the reference value of the intensity by the reference value. It is memorized.

  According to the present invention, even when the reference value of the intensity of the frequency component varies according to the frequency of each frequency component, the relationship data between the frequency of each frequency component and the attenuation rate from which the influence of the variation of the reference value is removed By using, it is possible to estimate the type of particles floating in the monitoring space without being affected by the fluctuation of the reference value.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the sound source unit generates a sound wave by applying a thermal shock to the air due to a temperature change of the heat generating unit accompanying energization of the heat generating unit. It is characterized by being.

  According to this configuration, the sound source unit has a flat frequency characteristic, and the frequency of the sound wave to be generated can be changed over a wide range. It is also possible to transmit a single-pulse sound wave with little reverberation from the sound source unit.

  According to a fourth aspect of the present invention, in the third aspect of the present invention, the sound source section includes the heating element portion formed on the one surface side of the base substrate, and the heating element portion and the base on the one surface side of the base substrate. It is characterized by having a thermal insulation layer comprising a porous layer provided between the substrate and thermally insulating the heating element and the base substrate.

  According to this configuration, since the heat insulating layer is made of a porous layer, the heat insulating property of the heat insulating layer is improved compared to the case where the heat insulating layer is made of a non-porous layer. The ratio of the sound pressure of the sound wave becomes high, and the power consumption can be reduced.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the sound wave including the plurality of frequency components transmitted by the sound source unit is a single-pulse sound wave. .

  According to this configuration, since the intensity difference between frequency components is small and a single-pulse sound wave having a power spectrum in which power is distributed over a relatively wide range of frequencies is transmitted from the sound source unit, the frequency component In the extracting means, the intensity difference is small and the intensity of a relatively wide range of frequency components can be extracted.

  According to a sixth aspect of the present invention, in any one of the first to fifth aspects of the present invention, the frequency component extraction means includes filter means for passing signals of the respective frequency components, and outputs the output of the receiving element. The intensity of each frequency component is extracted by passing through the filter means.

  According to this configuration, for example, it is possible to reduce the load of signal processing as compared with a configuration in which fast Fourier transform is performed on time-series data output from the receiving element and the intensity of each frequency component is extracted from the result.

  According to a seventh aspect of the present invention, in the sixth aspect of the present invention, the filter means is individually provided for each frequency component, and the frequency component extracting means distributes the output of the receiving element to the filter means. It has a distribution means.

  According to this configuration, the intensity of a plurality of frequency components can be extracted from the sound wave transmitted at one time from the sound source unit. It is possible to avoid the estimation accuracy of the type and concentration of the sound source from being lowered and the power consumption accompanying the transmission of the sound wave from being increased.

  The invention of claim 8 is characterized in that, in the invention of any one of claims 1 to 5, the frequency component extraction means extracts the intensity of each frequency component by fast Fourier transform.

  According to this configuration, it is possible to extract the intensities of a large number of frequency components. Therefore, the accuracy of particle type estimation can be improved by estimating the type of suspended particles based on the intensities of the numerous frequency components. it can. In addition, since the intensity of a plurality of frequency components can be extracted from the sound wave transmitted at one time from the sound source unit, the type and concentration of suspended particles can be caused by variations in the transmitted sound pressure when each sound wave is transmitted. Thus, it is possible to avoid the estimation accuracy of the signal from being lowered and the power consumption accompanying the transmission of the sound wave from increasing.

  According to a ninth aspect of the present invention, in the invention according to any one of the first to sixth aspects, the frequency component extracting means transmits the reception through a propagation path having a different path length in the monitoring space that is simultaneously transmitted from the sound source unit. It is characterized in that the intensity of each frequency component is extracted from each of a plurality of sound waves respectively propagated to the wave element.

  According to this configuration, the intensity of a plurality of frequency components can be extracted from the sound wave transmitted at one time from the sound source unit. It is possible to avoid the estimation accuracy of the type and concentration of the sound source from being lowered and the power consumption accompanying the transmission of the sound wave from being increased.

  Since the present invention estimates the type of particles floating in the monitoring space using the intensity of each frequency component extracted by the frequency component extracting means and the relational data stored in the storage means, While it is possible to estimate the type of particles being performed, there is an effect that it is not necessary to transmit a plurality of types of sound waves from the sound source unit.

  In the following embodiments, as an example of the suspended particle measurement system of the present invention, an example of measuring the concentration of smoke particles in the monitoring space for the purpose of determining whether or not a fire has occurred, is not limited to this example. The suspended particle measurement system of the present invention can be used to measure the type and concentration of various suspended particles (smoke particles, dust, steam, etc.) in a monitoring space.

(Embodiment 1)
As shown in FIG. 2, the suspended particle measurement system of the present embodiment includes a sound source unit 1 capable of transmitting ultrasonic waves, a control unit 2 that controls the sound source unit 1, and ultrasonic waves transmitted from the sound source unit 1. Receiving element 3 that detects the sound pressure of the signal, and a signal processing unit that measures the type and concentration of suspended particles present in the monitoring space between the sound source unit 1 and the receiving element 3 based on the output of the receiving element 3 4 is provided. Here, the sound source unit 1 and the wave receiving element 3 that transmit and receive ultrasonic waves are employed. However, the sound source unit 1 and the wave receiving element 3 are not limited to ultrasonic waves, but may be anything that transmits and receives sound waves. .

  Here, as shown in FIG. 2, the sound source unit 1 and the wave receiving element 3 are arranged to face each other on the one surface side of the circuit board 5 made of a disk-shaped printed board. A control unit 2 and a signal processing unit 4 are provided. In addition, a sound absorbing layer (not shown) for preventing the reflection of the ultrasonic wave transmitted from the sound source unit 1 is provided on the one surface of the circuit board 5, so that the super wave transmitted from the sound source unit 1 is provided. The sound wave can be prevented from being reflected by the circuit board 5 and entering the wave receiving element 3, and interference of the reflected wave can be prevented.

  In the present embodiment, a sound wave generating element that generates an ultrasonic wave by applying a thermal shock to air as described later is used as the sound source unit 1 to transmit an ultrasonic wave having a reverberation time shorter than that of a piezoelectric element. In addition, as the wave receiving element 3, a capacitance type microphone is used in which the Q value of the resonance characteristics is sufficiently smaller than that of the piezoelectric element and the generation period of the reverberation component included in the received wave signal is short.

  Here, as shown in FIG. 3, the sound source unit 1 includes a heat insulating layer (heat insulation) made of a porous silicon layer on one surface (upper surface in FIG. 3) side of a base substrate 11 made of a single crystal p-type silicon substrate. Layer) 12 is formed, and a heating element layer 13 made of a metal thin film is formed on the surface side of the heat insulating layer 12 as a heating element portion, and is electrically connected to the heating element layer 13 on the one surface side of the base substrate 11. A pair of pads 14 and 14 are formed. The planar shape of the base substrate 11 is a rectangular shape, and the planar shapes of the thermal insulating layer 12 and the heating element layer 13 are also rectangular. An insulating film (not shown) made of a silicon oxide film is formed on the surface of the base substrate 11 where the thermal insulating layer 12 is not formed on the one surface side.

  In the above-described sound source unit 1, when current is passed between the pads 14 and 14 at both ends of the heating element layer 13 to cause a sudden temperature change in the heating element layer 13, the air (medium) that is in contact with the heating element layer 13. A sudden temperature change (thermal shock) occurs (that is, a thermal shock is applied to the air in contact with the heating element layer 13). Accordingly, the air in contact with the heating element layer 13 expands when the temperature of the heating element layer 13 rises and contracts when the temperature of the heating element layer 13 decreases. Therefore, by appropriately controlling energization to the heating element layer 13 Ultrasonic waves propagating in the air can be generated. In short, the sound wave generating element constituting the sound source unit 1 generates an ultrasonic wave propagating through the medium by converting a rapid temperature change of the heat generating body layer 13 accompanying energization to the heat generating body layer 13 into expansion and contraction of the medium. Therefore, it is possible to transmit single-pulse ultrasonic waves with less reverberation compared to the case where ultrasonic waves are generated by mechanical vibration like a piezoelectric element.

In the sound source unit 1 described above, a p-type silicon substrate is used as the base substrate 11, and the heat insulating layer 12 is formed of a porous layer made of a porous silicon layer having a porosity of about 60 to about 70%. Therefore, a porous silicon layer serving as the thermal insulating layer 12 can be formed by anodizing a part of the silicon substrate used as the base substrate 11 in an electrolytic solution composed of a mixed solution of hydrogen fluoride and ethanol. (Here, the porous silicon layer formed by the anodic oxidation treatment contains a large number of nanocrystalline silicon composed of microcrystalline silicon having a crystal grain size on the order of nanometers). Since the porous silicon layer has a lower thermal conductivity and heat capacity as the porosity becomes higher, the thermal conductivity and heat capacity of the heat insulating layer 12 are made smaller than the heat conductivity and heat capacity of the base substrate 11, and heat insulation is performed. By making the product of the thermal conductivity and heat capacity of the layer 12 sufficiently smaller than the product of the thermal conductivity and heat capacity of the base substrate 11, the temperature change of the heating element layer 13 can be efficiently transmitted to the air. In addition, efficient heat exchange occurs between the heating element layer 13 and the air, and the base substrate 11 can efficiently receive the heat from the heat insulating layer 12 and release the heat of the heat insulating layer 12 to generate heat. It is possible to prevent heat from the body layer 13 from being accumulated in the heat insulating layer 12. Note that the porosity formed by anodizing a single crystal silicon substrate having a thermal conductivity of 148 W / (m · K) and a heat capacity of 1.63 × 10 ⁶ J / (m ³ · K) is 60%. The porous silicon layer is known to have a thermal conductivity of 1 W / (m · K) and a heat capacity of 0.7 × 10 ⁶ J / (m ³ · K). In this embodiment, the heat insulating layer 12 is composed of a porous silicon layer having a porosity of approximately 70%, the heat conductivity of the heat insulating layer 12 is 0.12 W / (m · K), and the heat capacity is 0.00. It is 5 × 10 ⁶ J / (m ³ · K).

  The heating element layer 13 is made of tungsten, which is a kind of refractory metal, but the material of the heating element layer 13 is not limited to tungsten, and for example, tantalum, molybdenum, iridium, aluminum, or the like may be adopted. In the sound source unit 1 described above, the thickness of the base substrate 11 is 300 to 700 μm, the thickness of the heat insulating layer 12 is 1 to 10 μm, the thickness of the heating element layer 13 is 20 to 100 nm, and the thickness of each pad 14. However, these thicknesses are only examples and are not particularly limited. Further, Si is adopted as the material of the base substrate 11, but the material of the base substrate 11 is not limited to Si, and for example, it can be made porous by anodic oxidation treatment of Ge, SiC, GaP, GaAs, InP or the like. Other semiconductor materials may be used, and in any case, a porous layer formed by making a part of the base substrate 11 porous can be used as the heat insulating layer 12.

As described above, the sound source unit 1 generates ultrasonic waves in accordance with the temperature change of the heating element layer 13 due to energization of the heating element layer 13 via the pair of pads 14 and 14. When the drive input waveform composed of the drive voltage waveform or the drive current waveform applied to is a sine wave waveform having a frequency of f1, for example, the frequency of the temperature oscillation generated in the heating element layer 13 is ideally the frequency of the drive input waveform f1. The frequency f2 is doubled, and an ultrasonic wave having a frequency approximately twice that of the drive input waveform f1 can be generated. That is, the above-described sound source unit 1 has a flat frequency characteristic and can change the frequency of the generated ultrasonic wave over a wide range. Further, in the sound source unit 1 described above, for example, a half-cycle solitary wave of a sine wave waveform is applied between the pair of pads 14 and 14 as a drive input waveform, so that a single-pulse ultrasonic wave of approximately one cycle with little reverberation is generated. Can be generated. By using such single-pulse ultrasonic waves, interference due to reflection is less likely to occur, so that the sound absorbing layer can be made unnecessary. Further, in the sound source unit 1, since the heat insulating layer 12 is formed of a porous layer, the heat insulating layer 12 is compared with a case where the heat insulating layer 12 is formed of a non-porous layer (for example, a SiO ₂ film). As a result, the heat generation efficiency is improved, the efficiency of ultrasonic generation is increased, and the power consumption can be reduced.

  Although not shown, the control unit 2 that controls the sound source unit 1 gives a drive input waveform to the sound source unit 1 to drive the sound source unit 1, and a control circuit that includes a microcomputer that controls the drive circuit; It consists of

  Further, as shown in FIG. 4, the capacitance type microphone constituting the wave receiving element 3 has a rectangular frame-shaped frame 31 formed by providing a window hole 31a penetrating in the thickness direction in the silicon substrate. And a cantilever-type pressure receiving portion 32 disposed on one surface side of the frame 31 so as to straddle two opposing sides of the frame 31. Here, a thermal oxide film 35, a silicon oxide film 36 covering the thermal oxide film 35, and a silicon nitride film 37 covering the silicon oxide film 36 are formed on one surface side of the frame 31, and one end of the pressure receiving portion 32. Is supported by the frame 31 via the silicon nitride film 37, and the other end faces the silicon nitride film 37 in the thickness direction of the silicon substrate. Further, a fixed electrode 33a made of a metal thin film (for example, a chromium film) is formed on the surface of the silicon nitride film 37 facing the other end of the pressure receiving portion 32, and the silicon nitride film 37 at the other end of the pressure receiving portion 32 is formed. A movable electrode 33b made of a metal thin film (for example, a chromium film) is formed on the opposite side of the opposite surface. A silicon nitride film 38 is formed on the other surface of the frame 31. The pressure receiving portion 32 is constituted by a silicon nitride film formed in a separate process from the silicon nitride films 37 and 38 described above.

  In the wave receiving element 3 composed of a capacitive microphone having the configuration shown in FIG. 4, a capacitor having the fixed electrode 33a and the movable electrode 33b as electrodes is formed, so that the pressure receiving portion 32 receives the pressure of the dense wave. As a result, the distance between the fixed electrode 33a and the movable electrode 33b changes, and the capacitance between the fixed electrode 33a and the movable electrode 33b changes. Therefore, if a DC bias voltage is applied between pads (not shown) provided on the fixed electrode 33a and the movable electrode 33b, a minute voltage change occurs between the pads according to the sound pressure of the ultrasonic waves. The sound pressure of ultrasonic waves can be converted into an electric signal.

  Here, the suspended particle measuring system of the present embodiment has the same basic configuration as the suspended particle measuring system described with reference to FIG. 15 in the column “Problems to be Solved by the Invention”, as shown in FIG. In addition, the signal processing unit 4 estimates particle type estimation means 41 for estimating the type of suspended particles existing in the monitoring space between the sound source unit 1 and the receiving element 3, and estimates the concentration of suspended particles in the monitoring space. Concentration estimation means 42, particle type estimation means 41, and storage means 44 that stores data used by concentration estimation means 42 are provided.

  That is, in this embodiment, the sound source unit 1 employs a configuration in which an ultrasonic wave including a plurality of frequency components is transmitted, and a frequency component that detects the intensity of each frequency component from the ultrasonic wave detected by the wave receiving element 3. An extraction means 40 is added to the signal processing unit 4. A specific example of the ultrasonic wave transmitted from the sound source unit 1 and a configuration example of the frequency component extraction unit 40 will be described later. Further, the particle type estimation unit 41 estimates the type of particles floating in the monitoring space using the intensity of each frequency component extracted by the frequency component extraction unit 40 and the relational data stored in the storage unit 44. In addition, since the concentration of suspended particles measured by the signal processing unit 4 is used to determine whether or not there is a fire, the concentration estimation unit 42 is configured so that the particles estimated by the particle type estimation unit 41 are smoke particles. In addition, it is assumed that the concentration of suspended particles in the monitoring space is estimated based on the attenuation amount from the reference value of the intensity of a specific frequency component (for example, 82 kHz).

  Further, the storage means 44 stores at least the reference value of the intensity of each frequency component extracted from the output of the wave receiving element 3 by the frequency component extracting means 40 (in the wave receiving element 3 in a state where no suspended particles exist in the monitoring space). The intensity of each frequency component extracted from the output of the receiving element 3 with respect to the received reference sound pressure), the type of suspended particles present in the monitoring space, and the frequency of each frequency component corresponding to the suspended particle concentration Data relating to the relative unit attenuation rate of the component intensity (data extracted from FIG. 17) and unit attenuation rate (data extracted from FIG. 16) at a specific frequency (for example, 82 kHz) with respect to smoke particles are stored. Yes.

  The signal processing unit 4 is configured by a microcomputer, and each of the means 40 to 44 is realized by mounting an appropriate program on the microcomputer. The signal processing unit 4 is also provided with an A / D converter for analog-digital conversion of the output signal of the wave receiving element 3.

  Hereinafter, an operation example of the suspended particle measurement system of the present embodiment will be described with reference to the flowchart of FIG. First, an ultrasonic wave including a plurality of frequency components is transmitted from the sound source unit 1, and the output of the wave receiving element 3 for the ultrasonic wave is measured by the signal processing unit 4 (step S11). The frequency component extraction means 40 extracts the intensity of each frequency component from the output of the receiving element 3, and the particle type estimation means 41 is stored in the storage means 44 with the intensity of each frequency component extracted by the frequency component extraction means 40. The attenuation rate of the intensity for each frequency component is obtained from the reference value (step S12), and the ratio of the attenuation rate of the frequency component having the center frequency of 20 kHz to the attenuation rate of the frequency component having the center frequency of 82 kHz is calculated (step S12). S13). The storage means 44 stores the relative unit attenuation rate at 20 kHz with respect to the relative unit attenuation rate at the output frequency of 82 kHz as the relational data of the frequency of each frequency component and the relative unit attenuation rate of the intensity of the frequency component. (In the case of FIG. 17, white smoke is 0, black smoke is 0.2, and steam is 0.5), and the particle type estimation means 41 stores the calculated ratio of the attenuation rate as storage means. Compared with the relational data stored in 44, the type of particle having the closest ratio of the attenuation rate in the relational data is estimated as the particle floating in the monitoring space (step S14). Here, if the estimated particles are smoke particles, the process proceeds to the processing by the concentration estimating means 42 (step S15). In this case, in the case of white smoke, as shown in FIG. 6, the relationship between the concentration of suspended particles measured by a dimming smoke densitometer and the attenuation rate of sound pressure is data that can be shown by a straight line. Therefore, the concentration estimation means 42 calculates the ratio of the attenuation rate of a specific frequency component (for example, 82 kHz) to the unit attenuation rate stored in the storage means 44 for the estimated particle type. When the value of the ratio is y, it is estimated that the smoke density in the monitoring space corresponds to the suspended particle density y [% / m] in the evaluation with the dimming smoke densitometer (step S16). The concentration of airborne particles estimated in step S16 is compared with a predetermined threshold (for example, the concentration of airborne particles that is 10% / m in the evaluation with a dimming smoke densitometer), and the airborne particle concentration estimated. Is less than the threshold value, it is determined that there is no fire. On the other hand, if it is greater than the threshold value, it is determined that there is a fire.

  In the above example, the particle type estimation means 41 uses the attenuation rate of the frequency component with the center frequency of 82 kHz and the attenuation rate of the frequency component with the center frequency of 20 kHz, but the combination is not limited to these frequency components. Alternatively, different combinations of frequency components may be used. Furthermore, the attenuation rate of more frequency components may be used, and in that case, the accuracy of estimation of the particle type can be improved. In the present embodiment, the concentration estimation unit 42 targets one frequency component as a specific frequency component. However, the concentration of suspended particles estimated for each frequency component with a plurality of frequency components as a specific frequency component is targeted. In this case, the accuracy of estimation of the concentration of suspended particles is improved.

  By the way, in this embodiment, in order to transmit an ultrasonic wave including a plurality of frequency components from the sound source unit 1, the control unit 2 drives the sound source unit 1 with a half-cycle isolated wave of a sine wave waveform as a drive input waveform. As given. As a result, a single-pulse (impulse) ultrasonic wave having approximately one cycle as shown in FIG. 7A is transmitted from the sound source unit 1. The power spectrum of this kind of single-pulse ultrasonic wave has a shape in which intensity (energy) is distributed over a wide range of frequencies with a frequency f0 corresponding to the pulse width as a center frequency as shown in FIG. 7B. . In short, by transmitting single-pulse ultrasonic waves from the sound source unit 1 as in the present embodiment, the sound source unit 1 transmits ultrasonic waves including a plurality of frequency components. Therefore, the frequency component extraction means 40 can extract the intensity of the frequency component for each frequency band indicated by B1 to B3 in FIG. 7B, for example.

  On the other hand, the power spectrum of a burst wave having a certain number of waves (for example, about 3 cycles) has a peak at a frequency f0 corresponding to the cycle, and the intensity is low in other frequency bands. Therefore, compared with the case where single pulse ultrasonic waves are used as in the present embodiment, the frequency components that can be extracted by the frequency component extraction means 40 have a large intensity difference and a narrow frequency range. When the ultrasonic wave from the sound source unit 1 becomes a continuous wave of a certain frequency f0 as shown in FIG. 8A, the ultrasonic power spectrum has a sharp peak at the frequency f0 as shown in FIG. 8B. In other frequency bands, the intensity is greatly reduced, and the frequency component extracting means 40 cannot extract the intensity of each frequency component.

  On the other hand, since the receiving element 3 uses a capacitance type microphone whose resonance characteristic Q value is sufficiently smaller than that of the piezoelectric element, a plurality of frequency components included in the ultrasonic wave from the sound source unit 1 are used. There is no great variation in sensitivity. However, since sensitivity decreases in a frequency band higher than the resonance frequency fc of the receiving element 3 as shown in FIG. 9B, the intensity of the frequency component is obtained by the frequency component extracting means 40 as shown in FIG. 9A. It is desirable to use the wave receiving element 3 having a resonance frequency that is higher than the frequency band B1 to B3 from which the noise is extracted. In FIGS. 7B, 8B, and 9 showing the power spectrum, and FIGS. 10 and 11 used in the following description, the horizontal axis represents frequency and the vertical axis represents intensity (power).

  Next, the configuration of the frequency component extraction unit 40 will be described.

  As an example, the sound source unit 1 transmits a single-pulse ultrasonic wave having a period of 3.33 μs (that is, equivalent to 300 kHz) as shown in FIG. It is assumed that the power spectrum of the ultrasonic wave to be formed has a peak at 300 kHz as shown in FIG. In this case, in order to extract the intensity of each frequency component in the frequency bands B1 to B3 in FIG. 11, as shown in FIG. 12, a first filter means (for example, a filter of 150 to 250 kHz (frequency band B1)) is passed. , A band pass filter) 45a, a second filter means 45b for passing a signal of 250 to 350 kHz (frequency band B2), and a third filter means 45c for passing a signal of 350 to 450 kHz (frequency band B3). Provided in the frequency component extraction means 40, the outputs of the first to third filter means 45a to 45c are extracted as the intensity of each frequency component.

  Here, the frequency component extraction means 40 is an amplifier Amp that amplifies the output of the wave receiving element 3, and a distribution means that distributes the output of the wave receiving element 3 amplified by the amplifier Amp substantially equally to each of the filter means 45a to 45c. 46, and the output of the wave receiving element 3 is output to the subsequent particle type estimation means 41 through the filter means 45a to 45c. Thereby, in the frequency component extraction means 40, the intensity | strength of a several frequency component can be extracted from the ultrasonic wave transmitted at once from the sound source part 1. FIG. Here, the filter means 45a to 45c may be realized by a program, but if realized by hardware, the load of signal processing can be reduced, and the speed of signal processing can be increased.

In the present embodiment, the example in which the relationship data between the frequency of each frequency component and the relative unit attenuation rate of the intensity is stored in the storage unit 44 is shown. However, depending on the type of suspended particles existing in the monitoring space in the first place. Since the attenuation amount (I ₀ -I _x ) from the reference value of the intensity of the frequency component changes for each frequency of the frequency component, the relational data stored in the storage unit 44 is the same as the frequency of each frequency component. Any data showing the relationship with the attenuation amount from the reference value of the intensity of the frequency component may be used. Instead of the above relative unit attenuation rate, for example, the attenuation amount from the reference value of the intensity of the frequency component or the frequency component It is also possible to store in the storage means 44 the attenuation rate obtained by dividing the attenuation amount from the reference value of the intensity by the reference value (I ₀ ) or the relation data adopting the unit attenuation rate.

  According to the suspended particle measurement system of the present embodiment described above, the frequency component extraction unit 40 extracts the intensity of each frequency component from the ultrasonic wave detected by the wave receiving element 3, and the particle type estimation unit 41 Since the type of suspended particles existing in the monitoring space is estimated using the intensity of each frequency component extracted by the frequency component extracting unit 40 and the relational data stored in the storage unit 44, the type of suspended particles can be estimated. However, it is not necessary to transmit a plurality of types of ultrasonic waves from the sound source unit 1.

  That is, when determining whether or not a fire has occurred by measuring the smoke concentration, the particle type estimation means 41 discriminates between smoke particles and steam by estimating the type of particles floating in the monitoring space. This makes it possible to reduce non-fire reports due to steam and is suitable for use in kitchens and bathrooms. In addition, it is possible to distinguish between dust and smoke particles floating when cleaning the room where the suspended particle measurement system is installed or when electrical work is performed on the back of the ceiling, thus reducing non-fire reports caused by dust. It is also possible. Since the particle type estimation means 41 can distinguish between white smoke particles and black smoke particles, it can also be used for identifying fire properties.

  In addition, it is only necessary to transmit one type of ultrasonic wave (in this case, a single pulsed ultrasonic wave) including a plurality of frequency components from the sound source unit 1, and a plurality of types of ultrasonic waves are transmitted from the sound source unit 1. Compared to the case, the cost of the sound source unit 1 and the control unit 2 can be kept low. Further, since the frequency component extraction means 40 extracts the intensity of a plurality of frequency components from the ultrasonic wave transmitted from the sound source unit 1 at a time, the transmission sound pressure varies when each ultrasonic wave is transmitted. There is also an advantage that it is possible to avoid the estimation accuracy of the type and concentration of suspended particles from being lowered and the power consumption accompanying the transmission of ultrasonic waves from being increased.

  Incidentally, the frequency component extracting means 40 is not limited to extracting the intensity of each frequency component by the filter means 45a to 45c as described above. For example, fast Fourier transform (FFT) is performed on the time series data of the output of the receiving element 3. And the intensity of each frequency component may be extracted from the result. In this case, it becomes easy to extract the intensities of a large number of frequency components, and by estimating the type of suspended particles based on the intensities of the large number of frequency components, it is possible to improve the accuracy of estimation of the particle type. . Further, there is also an advantage that the intensity of a plurality of frequency components can be extracted from the ultrasonic wave transmitted at one time from the sound source unit 1 without using the distributing means 46. However, in this case, the load of signal processing becomes larger than the configuration in which the intensity of each frequency component is extracted by the filter means 45a to 45c.

  The sound source unit 1 only needs to transmit an ultrasonic wave including a plurality of frequency components, and is not limited to the single-pulse ultrasonic wave as described above. An ultrasonic wave formed by superposing a plurality of different ultrasonic waves may be transmitted from the sound source unit 1.

(Embodiment 2)
The suspended particle measurement system of the present embodiment has substantially the same basic configuration as that of the first embodiment, and the configuration of the frequency component extraction means 40 is different from that of the suspended particle measurement system of the first embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  In the present embodiment, a plurality of propagation paths having different path lengths are formed between the sound source unit 1 and the wave receiving element 3, and the ultrasonic waves transmitted from the sound source unit 1 are branched into a plurality of propagation paths. The signal is received by the wave receiving element 3 through the path. Here, the frequency component extracting means 40 extracts the intensity of each frequency component from each of a plurality of ultrasonic waves transmitted simultaneously from the sound source unit 1 and propagated to the receiving element 3 through propagation paths having different path lengths. To do.

As an example of the present embodiment, as shown in FIG. 13A, a plurality of types of cylinders 6 a and 6 b having different propagation lengths of ultrasonic waves formed in an internal space are used as a sound source unit 1 and a wave receiving element 3. It is conceivable to intervene in parallel with each other. That is, between the sound source unit 1 and wave receiving element 3 as shown in FIG. 13 (a), the a cylindrical body 6a of a straight tubular pipe length L _1, a curved shape tube length L _{2 (>} L ₁ ) cylinders 6b are arranged in a plane orthogonal to the direction in which the sound source unit 1 and the receiving element 3 face each other, and the ultrasonic waves from the sound source unit 1 are applied to both the cylinders 6a and 6b. It branches so that it may pass through the internal space of each cylinder 6a, 6b. Accordingly, the ultrasonic wave transmitted from the sound source unit 1 is branched into the first and second ultrasonic waves Sw1 and Sw2 at the entrances (the left end face in FIG. 13A) of both the cylinders 6a and 6b. while being propagated in the wave receiving element 3 1 ultrasonic Sw1 is through the interior space of the cylindrical body 6a of tube length L ₁ (propagation path of the path length L _1), second ultrasonic Sw2 is tube length L ₂ It will be propagated to the wave receiving element 3 through the interior space of the cylindrical body 6b (the propagation path of the path length L _2). Thereafter, the frequency component extraction means 40 extracts the intensity of each frequency component from each of the ultrasonic waves Sw1 and Sw2.

Here, at the timing when each of the ultrasonic waves Sw1 and Sw2 arrives at the wave receiving element 3, a time difference Td corresponding to the difference between the path lengths L ₁ and L ₂ of the propagation path is generated as shown in FIG. 13B. This time difference Td is obtained by dividing the difference between the path lengths L ₁ and L ₂ by the speed of sound. In order to distinguish the ultrasonic waves Sw1 and Sw2 in the wave receiving element 3, it is necessary to keep the period during which the ultrasonic waves Sw1 and Sw2 are received by the wave receiving element 3 within the time difference Td.

That is, for example, the sound velocity at 340m / s, when the frequency of the ultrasonic wave transmitted from the sound source unit 1 is 100kHz, ultrasound period 10 [mu] s, since the wavelength 3.4 mm, the path length _L 1, _{L 2} When the difference is set to 68 mm, if the wave number of the ultrasonic wave exceeds 20, the ultrasonic waves overlap each other, and the wave receiving element 3 cannot distinguish the ultrasonic waves Sw1 and Sw2. Therefore, by adjusting the difference between the path lengths L ₁ and L ₂ and the wave number of the ultrasonic wave transmitted from the sound source unit 1 at one time, the ultrasonic waves do not overlap each other. When reducing the difference between the path lengths L ₁ and L ₂ in order to reduce the size of the suspended particle measurement system, as described in the first embodiment, It is useful to employ a sound source unit 1 that is configured to generate an ultrasonic wave by applying a thermal shock to air due to a temperature change and that can transmit a single-pulse ultrasonic wave with little reverberation.

  Furthermore, according to the configuration of FIG. 13A, since the cylinders 6 a and 6 b are provided between the sound source unit 1 and the wave receiving element 3, the ultrasonic waves transmitted from the sound source unit 1 are cylindrical. Diffusion is suppressed by passing through the internal spaces 6a and 6b, and a decrease in sound pressure due to diffusion of ultrasonic waves between the sound source unit 1 and the receiving element 3 can be suppressed. The sound pressure of the ultrasonic wave received by the wave receiving element 3 can be maintained high in the absence of noise, and the amount of change in the output of the wave receiving element 3 relative to the amount of change in the concentration of suspended particles becomes relatively large. The ratio is improved.

  In the example of FIG. 13, the sound source unit 1 and the receiving element 3 are arranged so as to face each opening end face of the cylinders 6 a and 6 b, and the inside of each cylinder 6 a and 6 b is a monitoring space. Therefore, for example, holes (not shown) for guiding suspended particles such as smoke particles are formed in the side surfaces along the longitudinal direction of the cylinders 6a and 6b.

  As another example of the present embodiment, one cylindrical body 6a is omitted, and the ultrasonic wave directly transmitted from the sound source unit 1 to the wave receiving element 3 is used as the first ultrasonic wave Sw1, A reflection surface along the direction in which the wave receiving elements 3 are arranged is formed on the side of the sound source unit 1 and the wave receiving element 3, and the ultrasonic wave directly transmitted from the sound source unit 1 to the wave receiving element 3 is referred to as the first ultrasonic wave Sw1. In addition, a configuration in which the ultrasonic wave reflected from the reflection surface and transmitted to the wave receiving element 3 after being transmitted from the sound source unit 1 is the second ultrasonic wave Sw2 is also conceivable.

  Alternatively, in order to form a plurality of propagation paths having different path lengths between the sound source unit 1 and the wave receiving element 3, the first and second reflecting surfaces 7a and 7b are replaced with the sound source unit 1 as shown in FIG. They may be arranged so as to face each other in the traveling direction of the ultrasonic waves transmitted from (the left-right direction in FIG. 14). Each of the reflection surfaces 7a and 7b reflects ultrasonic waves. The wave receiving element 3 is disposed on the first reflection surface 7a, and the sound source unit 1 is disposed on the second reflection surface 7b. Here, the frequency component extraction means 40 obtains the intensity of each frequency component from each of a plurality of ultrasonic waves having different numbers of times reflected by the reflection surfaces 7a and 7b before being propagated from the sound source unit 1 to the wave receiving element 3. Extract each one.

  That is, the ultrasonic wave directly transmitted from the sound source unit 1 to the wave receiving element 3 as shown in FIG. 14 is set as the first ultrasonic wave Sw1, and after being transmitted from the sound source unit 1, is reflected by the first reflecting surface 7a. Furthermore, an ultrasonic wave transmitted to the wave receiving element 3 by being reflected by the second reflecting surface 7b is referred to as a second ultrasonic wave Sw2. Thus, the path of the propagation path between the first ultrasonic wave Sw1 with 0 reflections on the reflection surfaces 7a and 7b and the second ultrasonic wave Sw2 with 2 reflections on the reflection surfaces 7a and 7b. The lengths are different, and the frequency component extraction means 40 calculates the intensity of each frequency component from each of the ultrasonic waves Sw1 and Sw2. Here, in order to enable the wave receiving element 3 to distinguish the ultrasonic waves Sw1 and Sw2, the difference in path length between the ultrasonic waves Sw1 and Sw2 and the wave number of the ultrasonic waves transmitted from the sound source unit 1 at once are adjusted. This is the same as the example of FIG. 13 in that the ultrasonic waves do not overlap each other.

  By the way, in the example of FIG. 14, each reflective surface 7a, 7b consists of a concave curved surface curved in the shape which collects a reflected wave on the other reflective surface 7a, 7b. Furthermore, the sound source unit 1 and the wave receiving element 3 are disposed on the reflecting surfaces 7a and 7b at positions where the reflected ultrasonic waves incident on the other reflecting surfaces 7a and 7b and reflected are focused.

  In short, the ultrasonic waves that reach the first reflecting surface 7a on the wave receiving element 3 side while spreading radially from the sound source unit 1 disposed on the second reflecting surface 7b are reflected by the first reflecting surface 7a. As a result, a parallel wave is generated with respect to the second reflecting surface 7b on the sound source unit 1 side, and then the light is reflected by the second reflecting surface 7b, thereby focusing at the position of the wave receiving element 3 on the first reflecting surface 7a. It will be. Therefore, even if the reflection on the reflecting surfaces 7a and 7b is repeated, the ultrasonic wave is not easily diffused. Therefore, a decrease in sound pressure due to the diffusion of the ultrasonic wave between the sound source unit 1 and the wave receiving element 3 can be suppressed. . As a result, the amount of change in the output of the wave receiving element 3 with respect to the amount of change in the concentration of suspended particles becomes relatively large, and the SN ratio is improved.

  In the suspended particle measurement system according to the present embodiment described above, the frequency component extraction unit 40 extracts the intensity of a plurality of frequency components from the ultrasonic waves transmitted simultaneously from the sound source unit 1. It can be avoided that the estimation accuracy of the type and concentration of suspended particles is lowered due to the variation in the transmitted sound pressure, and that the power consumption associated with the transmission of ultrasonic waves is increased. Further, since the frequency component extraction means 40 sequentially extracts the intensity of each frequency component from each of the ultrasonic waves Sw1 and Sw2 that have reached the wave receiving element 3 at different timings, the output of the wave receiving element 3 is output to a plurality of filter means 45a. ˜45c need not be passed simultaneously, and the distribution means 46 can be omitted.

  Other configurations and functions are the same as those in the first embodiment.

  By the way, the suspended particle measuring system of each of the above embodiments may include a diffusion preventing member that narrows the diffusion range of the ultrasonic wave from the sound source unit 1. That is, in the example of FIG. 13, the cylinders 6 a and 6 b provided between the sound source unit 1 and the wave receiving element 3 function as diffusion preventing members, but diffusion preventing members other than the cylinders 6 a and 6 b are applied. May be. For example, a pair of diffusion prevention plates can be used as a diffusion prevention member that narrows the diffusion range of ultrasonic waves from the sound source unit 1.

  Each diffusion prevention plate is a flat plate having a rectangular shape in plan view, and the pair of diffusion prevention plates are arranged substantially in parallel so that one surface faces each other. Here, the pair of diffusion prevention plates narrows the diffusion range of the ultrasonic wave by passing the ultrasonic wave from the sound source unit 1 through the space between the one surface facing each other. The sound source unit 1 and the wave receiving element 3 are sandwiched between the surfaces so that the ultrasonic waves from the sound source unit 1 are propagated through the space. By providing the diffusion preventing plate in this manner, the ultrasonic wave transmitted from the sound source unit 1 is prevented from diffusing by passing through the monitoring space surrounded by the one surface of the diffusion preventing plate. And a decrease in sound pressure due to diffusion of ultrasonic waves between the receiving element 3 and the wave receiving element 3 can be suppressed.

  In each of the above embodiments, the sound source unit 1, the control unit 2, the wave receiving element 3, and the signal processing unit 4 are provided on a single circuit board 5 and housed in a container (not shown). And a sound source side unit including the control unit 2 and a reception side unit including the wave receiving element 3 and the signal processing unit 4 are configured as separate bodies to constitute a separate suspended particle measurement system. It may be. Further, the sound source unit 1 is not limited to the sound wave generating element having the configuration shown in FIG. 3 described above. For example, a rapid temperature change of the heat generating unit accompanying energization of the heat generating unit with a thin aluminum plate as the heat generating unit. A sound wave may be generated by a thermal shock due to.

  Furthermore, in each of the above embodiments, if the control unit 2 transmits ultrasonic waves having a frequency having an insect-proofing effect from the sound source unit 1, it is possible to prevent insects from entering the monitoring space. , False measurement of suspended particles caused by insects can be reduced. Here, the control unit 2 periodically transmits ultrasonic waves having an insecticidal effect separately from the ultrasonic waves transmitted from the sound source unit 1 in order to estimate the type and concentration of suspended particles. Alternatively, in order to estimate the type and concentration of suspended particles, the ultrasonic wave transmitted from the sound source unit 1 may include a frequency component having an insecticidal effect.

It is a block diagram which shows the structure of Embodiment 1 of this invention. The principal part same as the above is shown, (a) is a schematic bottom view, (b) is a schematic side view. It is a schematic sectional drawing which shows the sound wave generation element used for the same as the above. The wave receiving element used for the above is shown, (a) is a partially broken schematic perspective view, and (b) is a schematic sectional view. It is a flowchart which shows the operation example same as the above. It is explanatory drawing which shows the relationship between the density | concentration of the suspended particle used for the same as the above, and the attenuation factor of a specific frequency component. (A) is a waveform diagram of ultrasonic waves from the sound source section, and (b) is a power spectrum diagram of (a). (A) is a waveform diagram of ultrasonic waves, (b) is a power spectrum diagram of (a). (A) is the power spectrum figure of the output of a receiving element, (b) is another power spectrum figure. (A) is a waveform diagram of ultrasonic waves from the sound source section, and (b) is a power spectrum diagram of (a). It is explanatory drawing of the extraction method of the intensity | strength of a frequency component same as the above. It is a schematic block diagram of the principal part same as the above. It is the schematic which shows the operation | movement of Embodiment 2 of this invention. It is the schematic which shows the other structural example same as the above. It is a block diagram which shows the structure of a prior art example. It is explanatory drawing which shows the relationship between the output frequency of a sound source part same as the above, and the unit attenuation rate of a sound pressure. It is explanatory drawing which shows the relationship between the output frequency of a sound source part same as the above, and a relative unit attenuation factor.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sound source part 2 Control part 3 Receiver element 4 Signal processing part 11 Base board 12 Thermal insulation layer 13 Heat generating body layer (heat generating body part)
40 Frequency component extraction means 41 Particle type estimation means 42 Concentration estimation means 44 Storage means 45a to 45c Filter means 46 Distribution means

Claims (9)

  Based on a sound source unit that transmits a sound wave including a plurality of frequency components, a control unit that controls the sound source unit, a receiving element that detects sound pressure of the sound wave transmitted from the sound source unit, and an output of the receiving element A signal processing unit for measuring the type and concentration of suspended particles existing in the monitoring space between the sound source unit and the receiving element, and the signal processing unit is configured to detect each frequency component from the sound wave detected by the receiving element. The frequency component extraction means for extracting the intensity, and the attenuation amount from the frequency and intensity reference value of each frequency component according to the type and concentration of the suspended particles existing in the monitoring space between the sound source unit and the receiving element Particles that estimate the type of particles floating in the monitoring space using the storage means that stores the relation data, the intensity of each frequency component extracted by the frequency component extraction means, and the relation data that is stored in the storage means Type estimation means and specific frequency components Suspended particle measuring system characterized by having a concentration estimation means for estimating the concentration of suspended particles in the monitoring space on the basis of the attenuation amount from the reference value of the degree.   2. The storage device according to claim 1, wherein the storage means stores relationship data between the frequency of each frequency component and an attenuation rate obtained by dividing an attenuation amount from a reference value of intensity by a reference value as the relationship data. Airborne particle measurement system.   3. The sound source unit according to claim 1, wherein the sound source unit generates a sound wave by applying a thermal shock to air due to a temperature change of the heat generating unit accompanying energization of the heat generating unit. Airborne particle measurement system.   The sound source unit is formed between the heat generating unit and the base substrate on the one surface side of the base substrate, and the heat generating unit and the base are formed on the one surface side of the base substrate. 4. The suspended particle measuring system according to claim 3, further comprising a thermal insulating layer comprising a porous layer that thermally insulates the substrate.   5. The suspended particle measurement system according to claim 1, wherein the sound wave including the plurality of frequency components transmitted by the sound source unit is a single-pulse sound wave. 6.   The frequency component extraction unit includes a filter unit that allows a signal of each frequency component to pass therethrough, and extracts the intensity of each frequency component by passing the output of the receiving element through the filter unit. The suspended particle measuring system according to any one of claims 1 to 5.   7. The filter means according to claim 6, wherein the filter means is provided separately for each frequency component, and the frequency component extraction means has distribution means for distributing the output of the receiving element to each filter means. Airborne particle measurement system.   6. The suspended particle measurement system according to claim 1, wherein the frequency component extraction unit extracts the intensity of each frequency component by fast Fourier transform. The frequency component extracting means transmits the intensity of each frequency component from each of a plurality of sound waves transmitted simultaneously from the sound source unit and propagated to the receiving element through propagation paths having different path lengths in the monitoring space. The suspended particle measuring system according to any one of claims 1 to 6, wherein the suspended particle measuring system is extracted.

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