JP4816524B2 - Fire detector - Google Patents

Description

  The present invention relates to a fire detector.

  2. Description of the Related Art Conventionally, as a fire detector that detects smoke generated in the event of a fire, a scattered light type smoke detector (see, for example, Patent Document 1) and a dimming smoke detector (see, for example, Patent Document 2) are known. Yes. Here, the scattered light type smoke detector is configured to receive light scattered by smoke particles of light irradiated to the monitoring space from a light projecting element made of a light emitting diode element by a light receiving element made of a photodiode. In addition, if smoke particles are present in the monitoring space, the amount of light received by the light receiving element is increased due to the generation of scattered light. Therefore, the presence or absence of smoke particles can be detected based on the amount of increase in the amount of light received by the light receiving element. On the other hand, the dimming smoke detector is configured so that light emitted from the light projecting element is directly received by the light receiving element, and smoke particles are present in the monitoring space between the light projecting element and the light receiving element. If it is present, the amount of light received by the light receiving element is reduced, and therefore the presence or absence of smoke particles can be detected based on the amount of light received by the light receiving element.

By the way, the scattered light type smoke detector needs to be equipped with a labyrinth body as a countermeasure against stray light, so when there is little air flow, the time until smoke particles enter the monitoring space in the event of a fire increases, and the response There was a problem with sex. In addition, there is a problem that the dimming smoke detector may generate a report due to the influence of background light (a non-fire report will be generated) even though no fire has occurred. . In addition, the separate-type dimming smoke detector needs to align the optical axes of the light projecting element and the light receiving element with high accuracy, and there is a problem that it takes a lot of work.
JP 2001-34862 A JP 61-33595 A

  In order to solve the problems of the photoelectric fire detector described above, the applicant of the present application has proposed a fire detector that detects the presence or absence of smoke using ultrasonic waves.

  As shown in FIG. 18, the fire detector includes a monitoring sound source unit 1 capable of transmitting ultrasonic waves, a control unit that controls the monitoring sound source unit 1, and a sound pressure of ultrasonic waves transmitted from the monitoring sound source unit 1. And a signal processing unit for determining the presence or absence of a fire based on the output of the monitoring receiving element 3. A signal processing unit configured to estimate a smoke concentration in a monitoring space between the monitoring sound source unit 1 and the monitoring receiving element 3 based on an attenuation amount from a reference value of the output of the monitoring receiving element 3; Smoke type judgment means for judging the presence or absence of a fire by comparing the estimated smoke density with a predetermined threshold value. That is, when smoke particles enter the monitoring space, the sound pressure of the ultrasonic wave from the monitoring sound source unit 1 decreases before reaching the monitoring wave receiving element 3, and the attenuation amount of the output of the monitoring wave receiving element 3 is the smoke in the monitoring space. Since it increases approximately in proportion to the concentration, it is possible to determine the presence or absence of a fire by estimating the smoke concentration based on this attenuation.

  This ultrasonic fire detector can eliminate the influence of background light, which is a problem with photoelectric fire detectors, and eliminates the need for a labyrinth that is required for scattered light smoke detectors. Smoke particles easily diffuse into the monitoring space in the event of a fire, improving responsiveness compared to scattered light smoke detectors and reducing non-fire reports compared to dimming smoke detectors. .

  However, in the ultrasonic fire detector described above, the ultrasonic wave transmitted from the monitoring sound source unit 1 in accordance with changes in the surrounding environment of the fire detector (for example, changes in temperature, humidity, atmospheric pressure, etc.). The sound pressure of the monitoring space changes, the attenuation rate of the ultrasonic wave when propagating through the medium air even when the smoke concentration is constant, or the sensitivity of the monitoring receiving element 3 changes. Regardless of the smoke concentration, the attenuation from the reference value of the output of the monitoring receiving element 3 may fluctuate, which may cause non-fire reports and misreports.

  In addition, the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit 1 changes according to the time-dependent change (for example, aging degradation) of the monitoring sound source unit 1 and the monitoring wave receiving element 3, Even if the sensitivity changes, the attenuation from the reference value of the output of the monitoring receiving element 3 may fluctuate regardless of the smoke density in the monitoring space, and there is a possibility that a non-fire report or a false alarm will occur.

  The present invention has been made in view of the above reasons, and in a configuration for determining the presence or absence of a fire based on the amount of attenuation of ultrasonic waves in a monitoring space, a fire detector capable of reducing non-fire reports and missed reports is provided. The purpose is to provide.

  According to the first aspect of the present invention, a monitoring sound source unit capable of transmitting ultrasonic waves to a monitoring space that communicates with an external space and allows airborne particles including smoke particles to enter from the external space, and an intrusion of airborne particles including smoke particles Detects the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit, the reference sound source unit capable of transmitting ultrasonic waves to the reference space where the sound is blocked, the control unit that controls the monitoring sound source unit and the reference sound source unit Monitoring receiving element, a reference receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the reference sound source unit, and a signal for determining the presence or absence of a fire based on the outputs of the monitoring receiving element and the reference receiving element A processing unit, and the signal processing unit is estimated by a smoke concentration estimation unit that estimates a smoke concentration of the monitoring space based on an attenuation amount from a reference value of an output of the monitoring receiving element, and a smoke concentration estimation unit. Smoke type judgment that judges whether there is a fire by comparing the smoke concentration with a predetermined threshold And having an output correction means for correcting the output of the monitoring wave receiving element based on stage and rate of change from the initial value of the output of the reference wave receiving devices.

  According to this configuration, the monitoring sound source unit capable of transmitting ultrasonic waves to the monitoring space that communicates with the external space and allows the floating particles including smoke particles to enter from the external space, and the invasion of floating particles including the smoke particles A reference sound source unit capable of transmitting an ultrasonic wave to the blocked reference space, a monitoring receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit, and a wave transmitted from the reference sound source unit An output correction means for correcting the output of the monitoring receiving element based on the rate of change from the initial value of the output of the reference receiving element. Therefore, even if the sound pressure of the ultrasonic wave transmitted from the monitoring sound source section changes or the smoke concentration is constant, according to changes in the surrounding environment of the fire detector or changes over time of the monitoring sound source section or monitoring receiving element The attenuation rate of the ultrasonic wave when propagating through the medium air changes or is received by monitoring Even if the sensitivity of the child may change, the influence of the output fluctuation of the monitoring receiving element due to these changes can be removed by correction by the output correction means, and non-fire and misreports can be avoided. Can be reduced.

  According to a second aspect of the present invention, in the first aspect of the invention, the monitoring sound source unit can transmit a plurality of types of ultrasonic waves having different frequencies, and the signal processing unit is configured to detect suspended particles existing in the monitoring space. Storage means for storing relational data between the output frequency of the monitoring sound source unit corresponding to the type and smoke density and the attenuation amount from the reference value of the output of the monitoring receiving element, and each of the waves transmitted from the monitoring sound source unit Particle type estimation means for estimating the type of particles floating in the monitoring space using the output of the monitoring receiving element for each ultrasonic wave of the frequency and the relational data stored in the storage means, The smoke concentration estimation means is configured to determine whether or not the monitoring space is based on an attenuation amount from a reference value of an output of the monitoring receiving element with respect to an ultrasonic wave of a specific frequency when the particles estimated by the particle type estimation means are smoke particles. Characterized by estimating smoke density To.

  According to this configuration, in the signal processing unit, in the particle type estimation unit, the output of the monitoring receiving element for each ultrasonic wave of each frequency transmitted from the monitoring sound source unit and the relational data stored in the storage unit The type of particles floating in the monitoring space is estimated, and when the particles estimated by the particle type estimation means are smoke particles, the smoke concentration estimation means Since the smoke concentration in the monitoring space is estimated based on the attenuation from the output reference value, the particle type identification means discriminates, for example, smoke particles and steam by estimating the type of particles floating in the monitoring space. Therefore, it is possible to reduce non-fire reports due to steam as compared with the scattered light smoke detector and the dimming smoke detector, and it is also suitable for use in the kitchen or bathroom.

  According to a third aspect of the present invention, in the second aspect of the present invention, the storage unit divides, as the relation data, an attenuation amount from an output frequency of the monitoring sound source unit and a reference value of the output of the monitoring receiving element by a reference value. It stores the relationship data with the attenuation rate.

  According to this invention, even when the reference value of the output of the monitoring receiving element fluctuates according to the output frequency of the monitoring sound source unit, the influence of the fluctuation of the output frequency of the monitoring sound source unit and the reference value is eliminated. By using the relationship data with the attenuation rate, 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 fourth aspect of the present invention, in the invention of the second or third aspect, the monitoring sound source unit is composed of a single sound wave generating element capable of transmitting the plurality of types of ultrasonic waves, and the control unit is a sound wave generating element. The monitoring sound source unit is controlled so that a plurality of types of ultrasonic waves are sequentially transmitted.

  According to this configuration, the monitoring sound source unit can be reduced in size and cost compared to a case where the monitoring sound source unit includes a plurality of sound wave generating elements capable of transmitting various ultrasonic waves.

  According to a fifth aspect of the present invention, in the invention according to any one of the first to fourth aspects, the monitoring sound source section and the reference sound source section are heated to the air due to a temperature change of the heat generating section accompanying energization to the heat generating section. It is characterized in that an ultrasonic wave is generated by giving an impact.

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

  The invention according to claim 6 is the invention according to claim 5, wherein the monitoring sound source unit and the reference sound source unit are formed on the one surface side of the base substrate, while the heating element portion is formed on one surface side of the base substrate. It has a heat insulating layer which is provided between the heat generating element and the base substrate and is composed of a porous layer which thermally insulates the heat generating 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 ultrasonic wave becomes high, and low power consumption can be achieved.

  According to a seventh aspect of the present invention, in any one of the first to sixth aspects of the present invention, a cylindrical shape is formed on a propagation path of an ultrasonic wave transmitted from the monitoring sound source unit and received by the monitoring receiving element. And a cylindrical body that narrows a diffusion range of the ultrasonic wave by passing the ultrasonic wave from the monitoring sound source unit through the internal space.

  According to this configuration, the cylindrical body that is formed in a cylindrical shape and that narrows the diffusion range of the ultrasonic wave by passing the ultrasonic wave from the monitoring sound source unit through the internal space is transmitted from the monitoring sound source unit and received by the monitoring receiving element. Since the ultrasonic wave from the monitoring sound source unit passes through the cylinder, diffusion is suppressed, and a decrease in sound pressure due to the diffusion of the ultrasonic wave can be suppressed. Therefore, the change amount of the output of the monitoring receiving element with respect to the change amount of the smoke density becomes relatively large, and the SN ratio is improved.

  The invention according to claim 8 is the invention according to claim 7, wherein the cylindrical body is divided into the monitoring space and the reference space by a partition wall along a longitudinal direction, and the monitoring space is provided on the monitoring space side. A communication hole having a size that allows airborne particles including smoke particles to pass therethrough, and the monitoring receiving element and the reference receiving element are arranged at one end surface in the longitudinal direction of the cylindrical body. The monitoring sound source unit and the reference sound source unit are arranged in the monitoring space and the reference space, respectively, and the monitoring sound source unit and the reference sound source unit are arranged on the other end surface in the longitudinal direction of the cylindrical body so as to straddle the monitoring space and the reference space. It consists of a single sound wave generating element.

  According to this configuration, since the monitoring sound source unit and the reference sound source unit are composed of a single sound wave generating element, the monitoring sound source unit and the reference sound source unit change over time in the same manner. Even if the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit changes, the influence of the output fluctuation of the monitoring receiving element caused by this change can be reliably removed by correction by the output correction means, Non-fire reports and missed reports can be reduced.

  The invention of claim 9 is the invention of any one of claims 1 to 8, wherein the reference space is surrounded by a blocking wall that blocks floating particles including smoke particles, and the blocking wall passes through the floating particles. It has a fine hole size that is not allowed to be communicated, and the reference space and the external space communicate with each other through the fine hole.

  According to this configuration, since the reference space and the external space are communicated with each other through a microscopic hole of a size that does not allow airborne particles including smoke particles to pass through, fire detection is performed while blocking the invasion of airborne particles into the reference space. Changes in the ambient environment of the vessel, such as humidity and atmospheric pressure, are also reflected in the reference space through the micropores, and the effects of output fluctuations in the monitoring receiver due to these changes are removed by correction with the output correction means Can reduce non-fire reports and misreports.

  In the present invention, the output correction means corrects the output of the monitoring receiving element based on the rate of change from the initial value of the output of the reference receiving element. The sound pressure of the ultrasonic wave transmitted from the monitoring sound source section changes according to the change over time of the wave receiving element, and the attenuation rate of the ultrasonic wave when propagating through the medium air changes even if the smoke concentration is constant. Even if the sensitivity of the monitoring receiver element may change, the influence of the output fluctuation of the monitoring receiver element due to these changes can be eliminated by correction by the output correction means, and non-fire There is an effect that it is possible to reduce reports and missed reports.

(Embodiment 1)
As shown in FIG. 1, the fire detector according to the present embodiment includes a monitoring sound source unit 1 capable of transmitting ultrasonic waves, a reference sound source unit 10 capable of transmitting ultrasonic waves, a monitoring sound source unit 1 and a reference sound source unit. 10, a control receiving unit 3 for detecting the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit 1, and a sound pressure of the ultrasonic wave transmitted from the reference sound source unit 10. A reference wave receiving element 30 and a signal processing unit 4 that determines the presence or absence of a fire based on outputs of the monitoring wave receiving element 3 and the reference wave receiving element 30 are provided.

  Here, as shown in FIG. 2, the monitoring sound source unit 1 and the monitoring wave receiving element 3 are arranged so as to be opposed to each other on the one surface side of the circuit board 5 made of a disk-shaped printed board, and similarly, the reference sound source unit 10 and the reference wave receiving element 30 are arranged to be opposed to each other on the one surface side of the circuit board 5, and the control unit 2 and the signal processing unit 4 are provided on the circuit board 5. Moreover, since the sound absorption layer (not shown) which prevents reflection of the ultrasonic wave transmitted from the monitoring sound source unit 1 or the reference sound source unit 10 is provided on the one surface of the circuit board 5, the monitoring sound source unit 1 and the ultrasonic wave transmitted from the reference sound source unit 10 can be prevented from being reflected by the circuit board 5 and incident on the monitoring wave receiving element 3 or the reference wave receiving element 30, thereby preventing interference of the reflected wave. This is particularly effective when a continuous wave is used as an ultrasonic wave transmitted from the monitoring sound source unit 1 or the reference sound source unit 10. Note that a sound insulating wall 6 (see FIG. 18) made of a sound insulating plate for preventing the ultrasonic waves generated outside the monitoring sound source unit 1 from entering the monitoring wave receiving element 3 may be provided around the monitoring wave receiving element 3. Good.

  In addition, a monitoring space Sp1 leading to an external space (outside air) around the fire detector is formed between the monitoring sound source unit 1 and the monitoring receiving element 3 to monitor the presence or absence of a fire, and a reference sound source unit Between reference numeral 10 and the reference receiving element 30, a reference space Sp <b> 2 in which intrusion of floating particles is blocked is formed by being surrounded by a blocking wall 7 that blocks floating particles including at least smoke particles. That is, the monitoring sound source unit 1 transmits ultrasonic waves to the monitoring space Sp1, and the reference sound source unit 10 transmits ultrasonic waves to the reference space Sp2.

  In this embodiment, each of the monitoring sound source unit 1 and the reference sound source unit 10 uses a sound wave generating element that generates an ultrasonic wave by applying a thermal shock to air as will be described later, thereby reverberating compared to a piezoelectric element. Reverberation included in the received signal so that ultrasonic waves having a short time are transmitted, and the Q value of the resonance characteristic is sufficiently smaller than that of the piezoelectric element in each of the monitoring receiving element 3 and the reference receiving element 30. A capacitive microphone with a short component generation period is used. Hereinafter, the configurations of the monitoring sound source unit 1 and the monitoring wave receiving element 3 will be described. However, the reference sound source unit 10 adopts the same structure as the monitoring wave receiving element 3 in the monitoring sound source unit 1 and the reference sound source unit 30. It shall be.

  As shown in FIG. 3, the monitoring sound source unit 1 includes a heat insulating layer (heat insulating layer) 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. 12 is formed, a heating element layer 13 made of a metal thin film is formed as a heating element portion on the surface side of the heat insulating layer 12, and a pair of the heating elements 13 electrically connected to the one surface side of the base substrate 11. 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 monitoring sound source unit 1 described above, 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) ) Abruptly changes in temperature (thermal shock) (that is, 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 that propagate in the air can be generated. In short, the sound wave generating element constituting the monitoring 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 monitoring sound source unit 1 described above, a p-type silicon substrate is used as the base substrate 11, and the thermal 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 heat insulating layer 12 is 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 includes 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 monitoring sound source unit 1 described above, the base substrate 11 has a thickness of 300 to 700 μm, the thermal insulating layer 12 has a thickness of 1 to 10 μm, the heating element layer 13 has a thickness of 20 to 100 nm, and the thickness of each pad 14. Although the thickness is 0.5 μm, these thicknesses are merely 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 monitoring sound source unit 1 generates an ultrasonic wave in accordance with a temperature change of the heating element layer 13 due to energization to the heating element layer 13 via the pair of pads 14 and 14. When the drive input waveform made up of the drive voltage waveform or drive current waveform applied to 13 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 f1 of the drive input waveform. Therefore, it is possible to generate an ultrasonic wave having a frequency substantially twice that of the drive input waveform f1. That is, the above-described monitoring sound source unit 1 has a flat frequency characteristic compared to the case where ultrasonic waves are generated by mechanical vibration like a piezoelectric element, and changes the frequency of the generated ultrasonic waves over a wide range. be able to. In the monitoring sound source unit 1 described above, for example, a half-cycle solitary wave having a sine wave waveform is applied as a drive input waveform between the pair of pads 14 and 14 to thereby generate a single-pulse ultrasonic wave with substantially one cycle with little reverberation. 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 monitoring sound source unit 1, since the heat insulating layer 12 is composed of a porous layer, the heat insulating layer 12 is compared with a case where the heat insulating layer 12 is made of a non-porous layer (for example, a SiO ₂ film). The heat insulation property of 12 is improved, the ultrasonic wave generation efficiency is increased, and the power consumption can be reduced.

  Although not shown, the control unit 2 that controls the monitoring sound source unit 1 and the reference sound source unit 10 gives drive input waveforms to the monitoring sound source unit 1 and the reference sound source unit 10, respectively. A driving circuit for driving and a control circuit composed of a microcomputer for controlling the driving circuit are configured.

  Further, as shown in FIG. 4, the capacitance type microphone constituting the monitoring receiving element 3 is a rectangular frame-like frame formed by providing a window hole 31a penetrating in the thickness direction in the silicon substrate. 31 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 monitoring wave receiving element 3 composed of a capacitance type microphone having the configuration shown in FIG. 4, a capacitor having the fixed electrode 33a and the movable electrode 33b as electrodes is formed. By receiving, the distance between the fixed electrode 33a and the movable electrode 33b changes, and the electrostatic 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.

  By the way, the signal processing unit 4 estimates the smoke concentration in the monitoring space Sp1 between the monitoring sound source unit 1 and the monitoring receiving element 3 based on the attenuation amount from the reference value of the output of the monitoring receiving element 3. The estimation unit 41, the smoke type determination unit 42 that compares the smoke concentration estimated by the smoke concentration estimation unit 41 with a predetermined threshold and determines the presence or absence of a fire, and the monitoring sound source unit 1 transmits ultrasonic waves. Sound speed detecting means 43 for obtaining the sound speed based on the time difference from when the ultrasonic wave is received by the monitoring wave receiving element 3, and the temperature of the monitoring space Sp1 is estimated based on the sound speed obtained by the sound speed detecting means 43. Temperature estimating means 44, thermal type judging means 45 for judging the presence or absence of a fire by comparing the temperature estimated by the temperature estimating means 44 with a specified temperature, and a change from the initial value of the output of the reference receiving element 30 Output for correcting the output of the monitoring receiving element 3 based on the rate And a positive means 40. The signal processing unit 4 is configured by a microcomputer, and each of the means 40 to 45 is realized by mounting an appropriate program on the microcomputer. In addition, the signal processing unit 4 is provided with an A / D converter that performs analog-digital conversion on the output signals of the monitoring receiving element 3 and the reference receiving element 30.

  The smoke density estimating means 41 estimates the smoke density based on the attenuation amount from the reference value of the output of the monitoring receiving element 3 that detects the sound pressure of the ultrasonic wave from the monitoring sound source unit 1. If the frequency of the ultrasonic wave transmitted from the unit 1 is constant, the attenuation amount increases substantially in proportion to the smoke concentration in the monitoring space Sp1, so the relationship data between the smoke concentration and the attenuation amount measured in advance is used. If the relational expression between the smoke density and the attenuation amount is obtained and stored based on this, the smoke density can be estimated from the attenuation amount using the above relational expression. The smoke type determination means 42 determines “no fire” when the smoke concentration estimated by the smoke concentration estimation means 41 is less than the above threshold value, while “no fire” when it exceeds the threshold value. And the fire detection signal is output to the control unit 2. Here, when the control unit 2 receives the fire detection signal from the smoke type determination means 42, the control unit 2 generates a drive input waveform to the monitoring sound source unit 1 so that an alarm sound including an audible sound wave is generated from the monitoring sound source unit 1. Control. Therefore, since the alarm sound can be generated from the monitoring sound source unit 1, it is not necessary to separately provide a speaker or the like for outputting the alarm sound, and the fire detector as a whole can be reduced in size and cost.

  Moreover, the sound speed detection means 43 calculates | requires sound speed using the distance between the monitoring sound source part 1 and the monitoring receiving element 3, and the said time difference. Further, the temperature estimating means 44 estimates the temperature of the monitoring space Sp1 from the sound speed using a well-known relational expression between the sound speed in the atmosphere and the absolute temperature. The thermal type determination means 45 determines “no fire” when the temperature estimated by the temperature estimation means 44 is lower than the above specified temperature, and determines “no fire” when above the specified temperature. The fire detection signal is output to the control unit 2. Here, even when the control unit 2 receives a fire detection signal from the thermal determination unit 45, the control unit 2 drives the monitoring sound source unit 1 so that an alarm sound including an audible sound wave is generated from the monitoring sound source unit 1. Control the input waveform. The sound speed detection means 43 periodically transmits ultrasonic waves of a predetermined frequency separately from the ultrasonic waves transmitted from the monitoring sound source unit 1 in order to estimate the smoke density, and the ultrasonic waves are received by the monitoring receiving element 3. The sound speed may be obtained based on the time difference until the sound is received, or the sound speed may be obtained using an ultrasonic wave transmitted from the monitoring sound source unit 1 in order to estimate the smoke density. The sound speed may be obtained based on a time difference from when the ultrasonic wave is transmitted from the reference sound source unit 10 until the ultrasonic wave is received by the reference wave receiving element 30.

  By the way, in the fire detector having the above-described configuration, changes in the surrounding environment (for example, changes in temperature, humidity, atmospheric pressure, etc.), or changes with time in the monitoring sound source unit 1 and the monitoring wave receiving element 3 (for example, deterioration over time). Accordingly, the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit 1 changes, the attenuation factor of the ultrasonic wave when propagating through the air as the medium changes even if the smoke concentration is constant, The output of the monitoring receiving element 3 may change regardless of the smoke density in the monitoring space Sp1 due to the sensitivity of the element 3 changing. Therefore, in the present embodiment, the output correction unit 40 corrects the output of the monitoring receiving element 3 based on the rate of change from the initial value of the output of the reference receiving element 30, whereby this in the monitoring receiving element 3. The influence of the output change of the seeds on the smoke density estimation means 41 is eliminated.

  Specifically, the output correction means 40 outputs the output (hereinafter referred to as “reference value”) of the reference receiving element 30 that detects the sound pressure of the ultrasonic wave transmitted from the reference sound source unit 10 to the reference space Sp2. In response, a correction coefficient based on the rate of change of the reference value from the initial value is held, and the output of the monitoring receiving element 3 corrected using the correction coefficient is output to the smoke density estimation means 41 in the subsequent stage. Here, the initial value of the reference value is, for example, a reference detected when the surrounding environment (for example, temperature, humidity, atmospheric pressure) is set to a predetermined state and no change with time has occurred (for example, before shipment). This value is stored in advance in the output correction means 40. Further, instead of using the detected reference value as an initial value, an equivalent initial value may be set (set on a program) at the design stage. Here, the control unit 2 and the signal processing unit 4 drive the reference sound source unit 10 and measure the reference value every time before driving the monitoring sound source unit 1 to detect the smoke density in the monitoring space Sp1, and calculate the correction coefficient. Accordingly, the correction coefficient is updated every time the smoke density is detected in the monitoring space Sp1.

  In the present embodiment, as an example, the monitoring sound source unit 1 and the reference sound source unit 10 are driven under the same conditions (for example, sound pressure and frequency of ultrasonic waves to be transmitted), and the monitoring wave receiving element 3 and the reference wave receiving element. 30 is used under the same conditions (for example, DC bias voltage), and the positional relationship between the monitoring sound source unit 1 and the monitoring receiving element 3 and the positional relationship between the reference sound source unit 10 and the reference receiving element 30 are set to be the same. As a result, when the monitoring space Sp1 does not enter the monitoring space Sp1 and the monitoring space Sp1 and the reference space Sp2 are in the same state (for example, temperature, humidity, atmospheric pressure), the output and reference of the monitoring receiving element 3 are referred to. The output of the wave receiving element 30 is made substantially the same. In this case, the initial value of the reference value and the reference value of the output of the monitoring receiving element 3 are substantially the same value. Here, although it is not necessary for the control unit 2 to drive the monitoring sound source unit 1 and the reference sound source unit 10 at the same time, the accumulated ultrasonic wave transmission time is the same between the monitoring sound source unit 1 and the reference sound source unit 10. To control each.

  In the reference space Sp2, since the intrusion of the floating particles is blocked by being surrounded by the blocking wall 7 that blocks the floating particles including smoke particles, the temperature of the reference space Sp2 is external space (outside air) and monitoring. Although it is the same as the space Sp1, smoke particles and steam do not enter the reference space Sp2, and the reference value is not attenuated from the initial value by smoke particles or steam. Furthermore, the reference space Sp2 of the present embodiment includes a filter (for example, a porous ceramic filter) in which a large number of micropores (not shown) having a size that does not allow air particles to pass through is formed in the blocking wall 7, so that the micropores The reference space Sp2 and the external space are communicated with each other. Therefore, in the reference space Sp2, in addition to the temperature, the humidity and the atmospheric pressure are the same as the external space and the monitoring space Sp1.

  Thereby, the rate of change from the initial value of the reference value, which is the output of the reference receiving element 30, changes in the surrounding environment (for example, temperature, humidity, atmospheric pressure), or the reference sound source unit 10 and the reference receiving element 30. It is determined according to the change with time (same as the change with time of the monitoring sound source unit 1 and the monitoring receiving element 3), and if the output of the monitoring receiving element 3 is corrected using the correction coefficient based on this change rate, the surrounding environment The output of the monitoring receiving element 3 excluding the influence of the change and the change with time can be obtained. Therefore, in the attenuation amount from the reference value of the output of the monitored receiving element 3 after correction used in the smoke density estimating means 41, the influence of the change in the surrounding environment and the change with time is excluded, and the smoke in the monitoring space Sp1 Only the concentration is reflected. Since the sound speed detecting means 43 is not affected by the output change of the monitor receiving element 3, the output of the monitor receiving element 3 before correction is input to the sound speed detecting means 43. You may make it input the output of the subsequent monitoring wave receiving element 3 into the sound speed detection means 43. FIG.

  Below, the operation example of the fire detector of this embodiment is demonstrated with reference to the flowchart of FIG. First, for example, before the shipment of the fire detector, the reference sound source unit 10 is driven to obtain an initial value of the reference value, and the initial value is held in the output correction means 40 (step S1). Then, after the fire detector is installed, before the monitoring sound source unit 1 is driven, the reference sound source unit 10 is driven to measure the reference value, and the correction coefficient is calculated based on the rate of change of the reference value from the initial value. (Step S2). Thereafter, the monitoring sound source unit 1 is driven to obtain the output from the monitoring receiving element 3, and this output is corrected by the output correction means 40 using the correction coefficient, whereby the output from the monitoring receiving element 3 is obtained. The influence of the change in the surrounding environment and the change with the passage of time is removed (step S3). Then, the smoke density estimating means 41 estimates the smoke density in the monitoring space Sp1 using the corrected output of the monitoring receiving element 3, and the smoke type judging means 42 judges the presence or absence of a fire (step S4). If step S4 is complete | finished, it will return to step S2 which calculates a correction coefficient, and will repeat the operation | movement of step S2-S4 mentioned above regularly.

  In this embodiment, the fire detector signal output from the smoke determination unit 42 or the thermal determination unit 45 is output to the control unit 2, but is not limited to the control unit 2. You may make it output to a notification apparatus.

  In the present embodiment, the monitoring sound source unit 1 and the reference sound source unit 10 have the same configuration, and the monitoring wave receiving element 3 and the reference wave receiving element 30 have the same configuration. The monitoring receiving element 3 and the reference receiving element 30 are used under the same conditions. However, the monitoring sound source unit 1, the reference sound source unit 10, the monitoring receiving element 3 and the reference are used. The receiving element 30 is configured separately, the monitoring sound source unit 1 and the reference sound source unit 10 are driven under different conditions, and the monitoring receiving element 3 and the reference receiving element 30 are used under different conditions. Also good. Further, for example, as shown in FIG. 6, the positional relationship between the monitoring sound source unit 1 and the monitoring receiving element 3 may be different from the positional relationship between the reference sound source unit 10 and the reference receiving element 30 (FIG. 6). In this example, the distance between the monitoring sound source unit 1 and the monitoring receiving element 3 is set larger than the distance between the reference sound source unit 10 and the reference receiving element 30).

  Furthermore, the fire detector of the present embodiment is configured to calculate the correction coefficient and update the correction coefficient by measuring the reference value every time the smoke density in the monitoring space Sp1 is detected. The configuration may be such that the correction coefficient is calculated once every time the smoke concentration in the space Sp1 is detected a plurality of times. For example, in an environment in which the correction coefficient hardly fluctuates, the correction coefficient is calculated (that is, updated). It is also possible to reduce power consumption by reducing the amount of power consumption.

  In the fire detector according to the present embodiment described above, the smoke density estimating means 41 determines the amount of noise between the monitoring sound source unit 1 and the monitoring receiving element 3 based on the attenuation from the reference value of the output of the monitoring receiving element 3. The smoke density in the monitoring space Sp1 is estimated, and the smoke type judging means 42 compares the smoke density estimated by the smoke density estimating means 41 with a predetermined threshold value to judge the presence or absence of a fire. Eliminates the effects of background light, which is a problem with photoelectric fire detectors such as detectors and dimming smoke detectors, and eliminates the need for labyrinth bodies required for scattered light smoke detectors This makes it easier for smoke particles to diffuse into the monitoring space Sp1 in the event of a fire, improving responsiveness compared to scattered light smoke detectors, and reducing non-fire reports compared to dimming smoke detectors. It becomes possible.

  In the present embodiment, the monitoring sound source unit 1 capable of transmitting ultrasonic waves to the monitoring space Sp1 and the monitoring receiving element 3 that detects the sound pressure of the ultrasonic waves transmitted from the monitoring sound source unit 1 are provided. In addition, a reference sound source unit 10 capable of transmitting an ultrasonic wave to the reference space Sp2 in which invasion of suspended particles is blocked, and a reference received wave for detecting the sound pressure of the ultrasonic wave transmitted from the reference sound source unit 10 And the output correction means 40 corrects the output of the monitoring receiving element 3 based on the rate of change from the initial value of the reference value, which is the output of the reference receiving element 30, so that the surroundings of the fire detector The sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit 1 changes according to the environmental change or the time-dependent change of the monitoring sound source unit 1 or the monitoring receiving element 3, or the air that is the medium even if the smoke concentration is constant. The attenuation factor of the ultrasonic wave when propagating changes, and the sensitivity of the monitoring receiving element 3 The influence of the output fluctuation of the monitoring receiving element 3 due to these changes can be removed by correction by the output correction means 40, and non-fire reports and misreports can be reduced. Can do.

  Furthermore, in the fire detector according to the present embodiment, the sound velocity detection means 43 determines the sound velocity based on the time difference from when the monitoring sound source unit 1 transmits an ultrasonic wave until the ultrasonic wave is received by the monitoring wave receiving element 3. The temperature estimation means 44 estimates the temperature of the monitoring space Sp1 based on the sound speed obtained by the sound speed detection means 43, and the thermal judgment means 45 estimates the temperature estimated by the temperature estimation means 44 and the specified temperature. Because it is judged whether there is a fire or not, it is possible to detect the fire even if the temperature rises at the time of fire without using a separate temperature detection element, and it becomes possible to detect the fire more reliably. .

(Embodiment 2)
The basic structure of the fire detector of the present embodiment is substantially the same as that of the first embodiment. As shown in FIG. 7, the cylinders 81 and 82 formed in a cylindrical shape are connected to the monitoring sound source unit 1 and the monitoring receiving element 3. And the fire detector of the first embodiment is different from the fire detector of the first embodiment in that it is disposed between the reference sound source unit 10 and the reference receiving element 30. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  As shown in FIG. 7, each cylindrical body 81, 82 is a straight tubular square tube, and one end surface in the longitudinal direction (left end surface in FIG. 7) is closed by each of the monitoring sound source unit 1 and the reference sound source unit 10. In addition, the other end surface (the right end surface in FIG. 7) is closed by each of the monitoring wave receiving element 3 and the reference wave receiving element 30, so that the supersonic waves from the monitoring sound source unit 1 and the reference sound source unit 10 are transmitted through the internal space. Propagate sound waves. That is, the internal space of the cylinder 81 provided between the monitoring sound source unit 1 and the monitoring wave receiving element 3 becomes the monitoring space Sp1, and the cylinder 82 provided between the reference sound source unit 10 and the reference wave receiving element 30 is provided. The internal space becomes the reference space Sp2. The cylinder 81 forming the monitoring space Sp1 is provided with a plurality of communication holes 81a having a size through which airborne particles including smoke particles pass, and the monitoring space Sp1 communicates with the external space through the communication holes 81a. Yes. On the other hand, the cylindrical body 82 forming the reference space Sp2 also serves as the blocking wall 7, and a filter (for example, a porous ceramic filter) in which a large number of micropores (not shown) having a size that does not allow floating particles to pass through is formed. Have at least some. By providing these cylinders 81 and 82, the ultrasonic waves transmitted from the monitoring sound source unit 1 and the reference sound source unit 10 are suppressed from being diffused by passing through the internal spaces of the cylinders 81 and 82, Therefore, a decrease in sound pressure due to ultrasonic diffusion can be suppressed.

Further, if the length dimensions and the opening shapes of both the cylinders 81 and 82 are the same, the shapes of the monitoring space Sp1 and the reference space Sp2 are substantially the same. Therefore, as described in the first embodiment, the monitoring sound source unit 1 and the reference sound source unit 10 have the same configuration, and the monitoring wave receiving element 3 and the reference wave receiving element 30 have the same structure. When the sound source unit 10 is driven under the same conditions and the monitoring wave receiving element 3 and the reference wave receiving element 30 are used under the same conditions, there is no invasion of suspended particles in the monitoring space Sp1, and the monitoring space Sp1 and the reference space Sp2 Is in the same state (for example, temperature, humidity, atmospheric pressure), the degree of coincidence between the output of the monitoring receiving element 3 and the output of the reference receiving element 30 increases. As a result, the accuracy of correcting the output of the monitoring receiving element 3 in the output correcting means 40 is improved, and the accuracy of estimating the smoke density in the smoke density estimating means 41 is improved. Here, for example, when it is assumed that the sensitivity decrease of an amount of Msens (0 ≦ Msens ≦ 1) has occurred in each of the monitoring receiving element 3 and the reference receiving element 30 due to a change in ambient environment or a change with time. Is Pref, the initial value of Pref is Pref0, the output of the monitoring receiving element 3 is Pmes, the reference value of Pmes is Pmes0, the Pmes corrected by the output correction means 40 is Pmes ', and the attenuation amount of Pmes' from Pmes0 is ΔPmes. given that,
Pref = (1−Msens) × Pref0
The correction coefficient (1-Msens) can be calculated from the equation of
Pmes ′ = Pmes × (1 / (1-Msens))
Pmes' is calculated from
ΔPmes = Pmes0−Pmes ′
ΔPmes can be obtained from

  In the present embodiment, an example is shown in which the cylinder 81 and the cylinder 82 are spaced apart and arranged in parallel on the one surface side of the circuit board 5, but the cylinder 81 and the cylinder 82 are in contact with each other. For example, as shown in FIG. 8, both cylindrical bodies 82, 82 may be arranged in the thickness direction of the circuit board 5 on one surface side of the circuit board 5.

  Further, as shown in FIG. 9, a cylinder 81 may be provided only between the monitoring sound source unit 1 and the monitoring receiving element 3. In the example of FIG. 9, the cylinder 81 is formed shorter than the interval between the monitoring sound source unit 1 and the monitoring receiving element 3, and each end surface in the longitudinal direction is formed from the monitoring sound source unit 1 and the monitoring receiving element 3. Both end surfaces in the longitudinal direction are opened by disposing them apart. Even in this case, since the diffusion of the ultrasonic waves from the monitoring sound source unit 1 is suppressed by passing through the cylinder 81, a decrease in sound pressure due to the diffusion of the ultrasonic waves can be suppressed. In this example, since the space between the monitoring sound source unit 1 or the monitoring receiving element 3 and the cylinder 81 is the monitoring space Sp1, the communication hole 81a is unnecessary.

  In the fire detector according to the present embodiment described above, the tube 81 is provided in the ultrasonic wave propagation path between the monitoring sound source unit 1 and the monitoring wave receiving element 3, so that the sound is transmitted from the monitoring sound source unit 1. Since the ultrasonic wave is prevented from diffusing by passing through the internal space of the cylinder 81, it is possible to suppress a decrease in sound pressure due to the diffusion of the ultrasonic wave between the monitoring sound source unit 1 and the monitoring wave receiving element 3. The sound pressure of the ultrasonic wave received by the monitoring receiving element 3 can be maintained high when there is no smoke particle in the monitoring space Sp1, and the amount of change in the output of the monitoring receiving element 3 relative to the amount of change in smoke concentration is relatively high. As a result, the S / N ratio is improved.

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

(Embodiment 3)
The basic structure of the fire detector of the present embodiment is substantially the same as that of the second embodiment, and the configuration of the cylinder, the configuration of the monitoring sound source unit 1 and the reference sound source unit 10 are different from the fire detector of the second embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 2, and description is abbreviate | omitted suitably.

  In the present embodiment, as the cylindrical body 8, as shown in FIG. 10, an internal space divided into a monitoring space Sp1 and a reference space Sp2 by a partition wall 8b along the longitudinal direction is adopted. The cylinder 8 has a communication hole 8a having a size that allows the suspended space including smoke particles to pass through the monitoring space Sp1 and the external space on the monitoring space Sp1 side, and includes the monitoring receiving element 3 and the reference receiving element. 30 are arranged in each of the monitoring space Sp1 and the reference space Sp2 on one end surface in the longitudinal direction (the right end surface in FIG. 10A). A portion of the cylindrical body 8 that forms the reference space Sp2 also serves as the blocking wall 7, and a filter (for example, a porous ceramic filter) in which a large number of micropores (not shown) having a size that does not allow floating particles to pass therethrough is formed. At least partially. Here, the monitoring sound source unit 1 and the reference sound source unit 10 are arranged on the other end surface in the longitudinal direction of the cylindrical body 8 (the left end surface in FIG. 10A) so as to straddle the monitoring space Sp1 and the reference space Sp2. It consists of a single sound wave generating element 1a. In FIG. 10B, illustration of the monitoring receiving element 3 and the reference receiving element 30 is omitted.

  Specific examples of this embodiment will be given below. The cylinder 8 is a rectangular tube having a square opening surface of 10 mm square, and the monitoring space Sp1 and the reference space Sp2 each have an opening surface of 5 mm × 10 mm by dividing the internal space into two equal parts. . Here, the surface (sending surface) of the heating element layer 13 that gives vibration to air as a medium in the sound wave generating element 1a is a 10 mm square shape. The sound wave generating elements 1a are arranged in such a manner that the surface of the heating element layer 13 is evenly distributed between the monitoring space Sp1 and the reference space Sp2 so that the ultrasonic waves are uniformly transmitted to the monitoring space Sp1 and the reference space Sp2. The In this case, the initial value of the reference value and the reference value of the output of the monitoring receiving element 3 are the same value. Here, if the output correction means 40 holds the initial value of the reference value that is the standard before the change with time, the ratio between the reference value and the initial value of the reference value and the output of the monitoring receiving element 3 From the ratio, it is possible to calculate the attenuation amount from the reference value of the output of the monitoring receiving element 3 from which the influence of the change in the surrounding environment and the change with time is removed. When the sound wave generating elements 1a are not evenly distributed to the monitoring space Sp1 and the reference space Sp2, or when the shapes of the monitoring space Sp1 and the reference space Sp2 are different from each other, the initial value of the reference value and the monitoring reception are received. What is necessary is just to calculate a correction coefficient using the ratio with the reference value of the output of the wave element 3. In the sound wave generating element 1a, a thermal insulating layer 12, a heating element layer 13, and a pair of pads 14 and 14 are formed on one surface of a single base substrate 11 on the monitoring space Sp1 side and the reference space Sp2 side, respectively. It may be what has been done.

  According to the above-described configuration, since the monitoring sound source unit 1 and the reference sound source unit 10 are composed of a single sound wave generating element 1a, the monitoring sound source unit 1 and the reference sound source unit 10 are similarly changed with time. Even if the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit 1 to the monitoring space Sp1 changes in accordance with the change over time of the unit 1, the same sound pressure change is transmitted from the reference sound source unit 10 to the reference space Sp2. It will also occur in the ultrasonic wave. Therefore, the influence of the output fluctuation of the monitoring receiving element 3 due to the change in the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit 1 can be reliably removed by the correction by the output correction means 40, and the non-fire report And false alarms can be reduced.

  Other configurations and functions are the same as those of the second embodiment.

(Embodiment 4)
The fire detector of the present embodiment has a basic configuration substantially the same as that of the first embodiment, and the configurations of the control unit 2 and the signal processing unit 4 are different as shown in FIG. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

By the way, the inventors of the present application show the output frequency and sound pressure of the monitoring sound source unit 1 as shown in FIG. 12 according to the type of suspended particles in the monitoring space Sp1 between the monitoring sound source unit 1 and the monitoring receiving element 3. The knowledge that the relationship with the unit attenuation rate is different was obtained. Here, the sound pressure (hereinafter referred to as the reference sound pressure) received by the monitoring receiving element 3 in the state where the suspended particles are not present in the monitoring space Sp1 is I ₀ , a dimming smoke densitometer (darkening smoke). the sound pressure of airborne particles of the concentration to be x% / m in the evaluation of in sensor) is reception by monitors wave receiving element 3 in the state they exist in the monitoring space Sp1 when the I _x, (I ₀ The value represented by −I _x ) / 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 Sp1. “I” in FIG. 12 is an approximate curve showing the relationship between the output frequency and the 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 This is an approximate curve (black triangle indicates measurement data) showing the relationship with the sound pressure unit attenuation rate. The unit attenuation rate shown here sets the distance between the monitoring sound source unit 1 and the monitoring receiving element 3 to 30 cm. It is data for each output frequency at the time. Each data at the right end in FIG. 12 is data when the output frequency is 82 kHz, and FIG. 13 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. 13, 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 knowledge, in the present embodiment, the control unit 2 controls the monitoring sound source unit 1 so that a plurality of types of ultrasonic waves having different frequencies are sequentially transmitted from the monitoring sound source unit 1, thereby performing signal processing. The unit 4 includes at least the reference output of the monitoring wave receiving element 3 (the output of the monitoring wave receiving element 3 with respect to the reference sound pressure), the type of the floating particles existing in the monitoring space Sp1 and the concentration of the floating sound source unit 1 Relationship data between the output frequency and the relative unit attenuation rate of the output of the monitoring receiving element 3 (data extracted from the above-described FIG. 13), unit attenuation rate at a specific frequency (for example, 82 kHz) with respect to smoke particles (the above-mentioned diagram) Storage means 48 storing data extracted from the monitoring sound source unit 1, the output of the monitoring receiving element 3 for each ultrasonic wave transmitted from the monitoring sound source unit 1, and the relational data stored in the storage means 48. For Particle type estimation means 46 for estimating the type of particles floating in the monitoring space Sp1, and ultrasonic waves having a specific frequency (for example, 82 kHz) when the particles estimated by the particle type estimation means 46 are smoke particles. The smoke density estimating means 47 for estimating the smoke density in the monitoring space Sp1 based on the amount of attenuation from the reference value of the output of the monitoring receiving element 3 with respect to the smoke density estimated by the smoke density estimating means 47 and a predetermined value Smoke judgment means 42 for judging the presence or absence of a fire by comparing with a threshold value is provided. Furthermore, the signal processing unit 4 corrects the output of the monitoring receiving element 3 based on the rate of change from the initial value of the output (reference value) of the reference receiving element 30 as described in the first embodiment. As a result, in the particle type estimation means 46 and the smoke concentration estimation means 47, after the correction by the output correction means 40 (that is, the influence of changes in the surrounding environment and changes over time is excluded). The output of the monitoring receiving element 3 is used.

  Below, the operation example of the fire detector of this embodiment is demonstrated with reference to the flowchart of FIG. First, a plurality of types of ultrasonic waves are sequentially transmitted from the monitoring sound source unit 1, and the output of the monitoring receiving element 3 for each ultrasonic wave is measured by the signal processing unit 4 (step S11). The particle type estimation means 46 obtains the sound pressure attenuation rate from the output of the monitoring receiving element 3 and the reference output stored in the storage means 48 for each output frequency (step S12), and the output frequency is 82 kHz. The ratio of the sound pressure attenuation rate at 20 kHz to the sound pressure attenuation rate is calculated (step S13). The storage means 48 stores the relative data at 20 kHz with respect to the relative unit attenuation rate when the output frequency is 82 kHz as the relational data between the output frequency of the monitoring sound source unit 1 and the relative unit attenuation rate of the output of the monitoring receiving element 3. The ratio of the target unit attenuation rate (in the case of FIG. 13, white smoke is 0, black smoke is 0.2, steam is 0.5) is stored, and the particle type estimation means 46 stores the calculated attenuation rate. The ratio is compared with the relational data stored in the storage means 48, and the kind of particle having the closest ratio of the attenuation rate in the relational data is estimated as the particle floating in the monitoring space Sp1 (step S14). Here, if the estimated particles are smoke particles, the process proceeds to the processing in the smoke concentration estimating means 47 (step S15). Here, in the case of white smoke, as shown in FIG. 15, the relationship between the smoke density measured by the dimming smoke densitometer and the attenuation rate of the sound pressure is data that can be shown by a straight line, and other particles Therefore, the smoke density estimation means 47 is stored in the storage means 48 of the attenuation rate of the output of the monitoring receiving element 3 for the ultrasonic wave of a specific frequency (for example, 82 kHz) for the estimated particle type. A ratio with respect to the unit attenuation rate is calculated, and when the value of the ratio is y, it is estimated that the smoke density in the monitoring space Sp1 corresponds to the smoke density y% / m in the evaluation with the dimming smoke densitometer (step S16). . The smoke type determination means 42 compares the smoke density estimated in step S16 with a predetermined threshold value (for example, a smoke density that is 10% / m in the evaluation with the dimming smoke densitometer), and the estimated smoke. When the concentration is less than the above threshold, it is determined that “no fire”, while when it is equal to or greater than the above threshold, it is determined that “fire exists” and a fire detection signal is output to the control unit 2.

  In the above example, the particle type estimation means 46 uses the attenuation rate when the output frequency is 82 kHz and the attenuation rate when the output frequency is 20 kHz. However, the present invention is not limited to the combination of these output frequencies, and different combinations are possible. An output frequency may be used. Furthermore, attenuation rates for more output frequencies may be used, and in that case, the accuracy of estimation of the particle type can be improved. In this embodiment, the smoke density estimation means 47 targets one frequency as the specific frequency, but targets a plurality of frequencies as the specific frequency, and obtains an average value of the smoke density estimated for each specific frequency. In this case, the accuracy of smoke density estimation is improved. The signal processing unit 4 is constituted by a microcomputer, and the output correction means 40, the particle type estimation means 46, the smoke concentration estimation means 47, and the smoke type determination means 42 are loaded with appropriate programs in the microcomputer. Is realized. In addition, the signal processing unit 4 is provided with an A / D converter that performs analog-digital conversion on the output signals of the monitoring receiving element 3 and the reference receiving element 30.

  Here, the monitoring sound source unit 1 uses one of the sound wave generating elements described in the first embodiment, and the above-described control unit 2 sequentially changes the frequency of the drive input waveform applied to the monitoring sound source unit 1. A plurality of types of ultrasonic waves having different frequencies are sequentially transmitted from the monitoring sound source unit 1. Here, the control unit 2 changes the frequency of the ultrasonic wave transmitted from the monitoring sound source unit 1 from the lower limit frequency (for example, 20 kHz) to the upper limit frequency (for example, 82 kHz) in a predetermined frequency range (for example, 20 kHz to 82 kHz). Let In the present embodiment, the control unit 2 is configured to control the monitoring sound source unit 1 so that four types of ultrasonic waves having different frequencies are sequentially transmitted from the monitoring sound source unit 1. The frequency of the ultrasonic wave transmitted from 1 is not limited to four types, but may be a plurality of types. For example, if two types are used, the control unit 2 and the control unit 2 are compared with the case where three or more types of ultrasonic waves are sequentially transmitted. The burden on the signal processing unit 4 can be reduced, and the control unit 2 and the signal processing unit 4 can be simplified. In the present embodiment, since the sound wave generating element described in the first embodiment is used as the monitoring sound source unit 1 as described above, the ultrasonic waves sequentially transmitted can be converted into ultrasonic waves having different frequencies. Cost reduction can be achieved as compared with the case where a plurality of piezoelectric elements having different resonance frequencies are used as the sound source unit 1 and continuous wave ultrasonic waves are transmitted from each piezoelectric element.

  In the present embodiment, the control unit 2 and the signal processing unit 4 also transmit ultrasonic waves from the reference sound source unit 10 at the same frequency as the monitoring sound source unit 1 each time before transmitting various types of ultrasonic waves from the monitoring sound source unit 1. Is transmitted, the reference value is measured, and the correction coefficient is calculated. Therefore, the reference sound source unit 10 also uses one of the sound wave generating elements described in the first embodiment, and the control unit 2 sequentially changes the frequency of the drive input waveform applied to the reference sound source unit 10 to thereby change the reference sound source. A plurality of types of ultrasonic waves having different frequencies are sequentially transmitted from the unit 10. Here, the control unit 2 sets the frequency of the ultrasonic wave transmitted from the reference sound source unit 10 to the lower limit frequency (for example, 20 kHz) of the ultrasonic frequency range (for example, 20 kHz to 82 kHz) to be transmitted from the monitoring sound source unit 1. To an upper limit frequency (for example, 82 kHz). In this embodiment, by using the sound wave generating element described in the first embodiment as the reference sound source unit 10 as described above, a plurality of piezoelectric elements having different resonance frequencies as the reference sound source unit 10 as in the monitoring sound source unit 1. The cost can be reduced compared to the case where continuous wave ultrasonic waves are transmitted from each piezoelectric element using the.

In the present embodiment, the example in which the relation data between the output frequency of the monitoring sound source unit 1 and the relative unit attenuation rate of the output of the monitoring receiving element 3 is stored in the storage unit 48 is shown. Since it is the amount of attenuation (I ₀ −I _x ) from the reference value of the output of the monitoring receiving element 3 that changes for each output frequency of the monitoring sound source unit 1 according to the type of suspended particles present, the storage means 48 The relational data stored in the above-mentioned data may be data indicating the relation between the output frequency of the monitoring sound source unit 1 and the attenuation amount from the reference value of the output of the monitoring receiving element 3, and instead of the above-mentioned relative unit attenuation rate. Thus, for example, the attenuation amount from the reference value of the output of the monitoring receiving element 3, the attenuation rate obtained by dividing the attenuation amount from the reference value of the output of the monitoring receiving element 3 by the reference value (I ₀ ), or Stores the relational data adopting the unit attenuation rate in the storage means 48. It may be so that.

  In the fire detector of the present embodiment described above, the particle type estimation unit 46 stores the output of the monitoring receiving element 3 for each ultrasonic wave transmitted from the monitoring sound source unit 1 and the storage unit 48. Is used to estimate the type of particles floating in the monitoring space Sp1, and when the particles estimated by the particle type estimation means 46 are smoke particles, the smoke density estimation means 47 The smoke density in the monitoring space Sp1 is estimated on the basis of the attenuation amount from the reference value of the output of the monitoring receiving element 3 with respect to the ultrasonic wave, and the smoke estimated by the smoke density estimating means 47 in the smoke type judging means 42 Since the presence of a fire is judged by comparing the concentration with a predetermined threshold, the influence of background light, which is a problem with photoelectric fire detectors such as scattered light smoke detectors and dimming smoke detectors, is considered. Can be lost and scattered Can eliminate the labyrinth required for a smoke detector, improve responsiveness compared to a scattered-light smoke detector, and reduce non-fire reports compared to a low-light smoke detector become. In addition, since the particle type estimation means 46 can identify the smoke particles and steam by estimating the type of particles floating in the monitoring space Sp1, the scattered light smoke detector and the dimming smoke detector. It is possible to reduce non-fire reports due to steam as compared with the above, and it is also suitable for use in the kitchen or bathroom. Further, since the white smoke particles and the black smoke particles can be discriminated by the particle type estimation means 46, it is also possible to use it for identifying the nature of the fire. In addition, it is possible to distinguish between dust and smoke particles floating when cleaning the room where the fire detector is installed or for electrical work behind the ceiling, so reduce non-fire reports caused by dust. Is also possible.

  By the way, in this embodiment, the monitoring sound source unit 1 and the reference sound source unit 10 are each configured by a single sound wave generating element, and the frequency of the drive input waveform that the control unit 2 gives to each of the monitoring sound source unit 1 and the reference sound source unit 10 is determined. By sequentially changing, a plurality of types of ultrasonic waves having different frequencies are sequentially transmitted from each of the monitoring sound source unit 1 and the reference sound source unit 10, but as shown in FIG. The monitoring sound source unit 1 and the reference sound source unit 10 may be configured by the sound wave generating elements 1a and 10a, respectively. In this case, an element that generates ultrasonic waves by mechanical vibration, such as a piezoelectric element, is used as each of the sound wave generation elements 1a and 10a, and the sound wave generation elements 1a and 10a are driven at their respective resonance frequencies for monitoring. The sound pressure of the ultrasonic wave transmitted from each of the sound source unit 1 and the reference sound source unit 10 can be increased to contribute to the improvement of the SN ratio. In addition to sequentially driving each of the sound wave generating elements 1a and 10a to sequentially transmit a plurality of types of ultrasonic waves, the plurality of sound wave generating elements 1a and 10a are simultaneously driven to simultaneously transmit a plurality of types of ultrasonic waves. It can also be made to wave.

  Further, as shown in FIG. 16, an individual monitoring receiving element 3 and a reference receiving element 30 may be provided for each of the sound wave generating elements 1 a and 10 a. In this case, the monitoring receiving element 3 In addition, a piezoelectric element having a relatively large resonance characteristic Q value is used for each of the reference receiving elements 30 and each of the monitoring receiving elements 3 and each of the reference receiving elements 30 is used for receiving ultrasonic waves having the respective resonance frequencies. Thereby, the sensitivity of the monitoring receiving element 3 and the reference receiving element 30 can be improved. In this way, each of the monitoring sound source unit 1 and the reference sound source unit 10 is constituted by a plurality of sound wave generating elements 1a and 10a, and the individual monitoring wave receiving element 3 and reference wave receiving for each of the sound wave generating elements 1a and 10a. When the element 30 is provided, the sound wave generating element 1a and the monitoring wave receiving element 3 constituting the monitoring sound source unit 1, and the sound wave generating element 10a and the reference wave receiving element 30 constituting the reference sound source part 10 are respectively shown in FIG. As shown, the circuit boards 5 are arranged to be opposed to each other on the one surface side. Furthermore, if the plurality of sound wave generating elements 1a and 10a are simultaneously driven to simultaneously transmit a plurality of types of ultrasonic waves, the attenuation amounts of the sound pressures of the plurality of types of ultrasonic waves can be detected at the same time. Detecting the attenuation of sound pressure for multiple types of ultrasonic waves without being affected by short-term changes in Sp1 over time (for example, changes in the concentration of suspended particles), and accurately estimating the type of suspended particles and smoke concentration Can do. It is also conceivable that the sound wave generating element 1a constituting the monitoring sound source unit 1 is also used as the monitoring wave receiving element 3, and the sound wave generating element 10a constituting the reference sound source unit 10 is also used as the reference wave receiving element 30. In this case, although a reflection surface for reflecting the ultrasonic wave transmitted from each of the sound wave generation elements 1a and 10a toward the sound wave generation element is required, the cost can be reduced by reducing the number of elements.

  Furthermore, in this embodiment, before transmitting various ultrasonic waves from the monitoring sound source unit 1, an example is shown in which the reference value is measured by transmitting ultrasonic waves from the reference sound source unit 10 and the correction coefficient is calculated. However, the correction coefficient may be calculated once every time a plurality of types of ultrasonic waves are transmitted from the monitoring sound source unit 1. For example, in an environment where the correction coefficient does not fluctuate, the correction coefficient is calculated. It is also possible to reduce power consumption by reducing the frequency of (that is, updating). In this case, it is not necessary to transmit a plurality of types of ultrasonic waves from the reference sound source unit 10, and the correction coefficient is calculated based on the amount of change from the initial value of the reference value for ultrasonic waves of a specific frequency (for example, 82 kHz). You can do it.

  Other configurations and functions are the same as those in the first embodiment. For example, also in the fire detector of the present embodiment, the sound speed detecting means 43, the temperature is added to the signal processing unit 4 as in the first embodiment shown in FIG. An estimation unit 44 and a thermal type determination unit 45 may be provided.

  Moreover, in each said embodiment, if the control part 2 transmits the ultrasonic wave of the frequency which has an insect-proof effect from the monitoring sound source part 1, it can prevent that an insect penetrate | invades into the said monitoring space Sp1. Can reduce non-fire reports caused by insects. Here, the control unit 2 periodically transmits ultrasonic waves having a frequency having an insect-proofing effect separately from the ultrasonic waves having a frequency transmitted from the monitoring sound source unit 1 in order to estimate the smoke density. Alternatively, the frequency of the ultrasonic wave transmitted from the monitoring sound source unit 1 in order to estimate the smoke density may be set to a frequency having an insecticidal effect. Further, the monitoring sound source unit 1 and the reference sound source unit 10 are not limited to the sound wave generating elements having the configuration shown in FIG. 3 described above. For example, a heating element associated with energization of the heating element unit using a thin aluminum plate as a heating element unit. A sound wave may be generated by a thermal shock caused by a rapid temperature change of the part.

It is a block diagram which shows the structure of Embodiment 1 of this invention. It is a schematic bottom view which shows a structure same as the above. It is a schematic sectional drawing which shows the sound wave generation element used for the same as the above. The monitoring receiving element used for the above is shown, (a) is a schematic perspective view with a part broken, and (b) is a schematic sectional view. It is a flowchart which shows the operation example same as the above. It is a schematic bottom view which shows the other example same as the above. It is a schematic bottom view which shows the structure of Embodiment 2 of this invention. It is a schematic side view which shows the other example same as the above. It is a schematic bottom view which shows another example same as the above. The structure of Embodiment 3 of this invention is shown, (a) is a schematic side view, (b) is a schematic slope view of the principal part. It is a block diagram which shows the structure of Embodiment 4 of this invention. It is explanatory drawing which shows the relationship between the output frequency of a monitoring 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 monitoring sound source part same as the above, and a relative unit attenuation factor. It is a flowchart which shows the operation example same as the above. It is explanatory drawing which shows the relationship between smoke density same as the above and the attenuation factor of the ultrasonic wave of a specific frequency. It is a block diagram which shows the other example same as the above. It is a schematic bottom view which shows a structure same as the above. A prior art example is shown, (a) is a schematic bottom view, and (b) is a schematic side view.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Monitoring sound source part 1a Sound wave generation element 2 Control part 3 Monitoring wave receiving element 4 Signal processing part 7 Blocking wall 8 Cylindrical body 8a Communication hole 8b Partition wall 10 Reference sound source part 10a Sound wave generation element 11 Base substrate 12 Thermal insulation layer 13 Heating element Layer (heating element)
30 Reference wave receiving element 40 Output correction means 41 Smoke density estimation means 42 Smoke type judgment means 46 Particle type estimation means 47 Smoke density estimation means 48 Storage means 81, 82 Cylindrical body 81a Communication hole Sp1 Monitoring space Sp2 Reference space

Claims (9)

  A monitoring sound source unit that can transmit ultrasonic waves to a monitoring space that communicates with the external space and allows airborne particles including smoke particles to enter from the external space, and a reference space where the invasion of airborne particles including smoke particles is blocked In contrast, a reference sound source unit capable of transmitting ultrasonic waves, a control unit that controls the monitoring sound source unit and the reference sound source unit, a monitoring receiving element that detects the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit, A reference receiving element that detects the sound pressure of the ultrasonic wave transmitted from the reference sound source unit, and a signal processing unit that determines the presence or absence of a fire based on the output of the monitoring receiving element and the reference receiving element. The processing unit is configured to estimate a smoke density in the monitoring space based on an attenuation amount from a reference value of the output of the monitoring receiving element, a smoke density estimated by the smoke density estimating means, and a predetermined threshold value Smoke type judgment means for judging the presence or absence of fire by comparing with the reference receiving element Fire detector and having an output correction means for correcting the output of the monitoring wave receiving element based on a rate of change from the initial value of the output.   The monitoring sound source unit can transmit a plurality of types of ultrasonic waves having different frequencies, and the signal processing unit outputs an output frequency of the monitoring sound source unit according to the type of suspended particles present in the monitoring space and the smoke concentration And storage means for storing the relationship data between the amount of attenuation from the reference value of the output of the monitoring receiving element, the output of the monitoring receiving element for each ultrasonic wave transmitted from the monitoring sound source unit, and Particle type estimation means for estimating the type of particles floating in the monitoring space using the relational data stored in the storage means, and the smoke concentration estimation means is estimated by the particle type estimation means 2. The smoke density of the monitoring space is estimated based on an attenuation amount from a reference value of the output of the monitoring receiving element with respect to an ultrasonic wave having a specific frequency when the detected particles are smoke particles. Fire detector.   The storage means stores, as the relation data, relation data between an output frequency of the monitoring sound source unit and an attenuation rate obtained by dividing an attenuation amount from a reference value of the output of the monitoring receiving element by a reference value. The fire detector according to claim 2, wherein   The monitoring sound source unit is composed of a single sound wave generating element capable of transmitting the plurality of types of ultrasonic waves, and the control unit is configured to transmit the plurality of types of ultrasonic waves sequentially from the sound wave generating elements. 4. The fire sensor according to claim 2, wherein the fire detector is controlled.   2. The monitoring sound source unit and the reference sound source unit generate ultrasonic waves by applying a thermal shock to air due to a temperature change of the heat generating unit accompanying energization of the heat generating unit. The fire detector according to any one of claims 4 to 4.   The monitoring sound source unit and the reference sound source unit are provided between the heat generating unit and the base substrate on the one surface side of the base substrate, while the heat generating unit is formed on one surface side of the base substrate. 6. The fire detector according to claim 5, further comprising a heat insulating layer made of a porous layer that thermally insulates the heating element portion and the base substrate.   On the propagation path of the ultrasonic wave transmitted from the monitoring sound source unit and received by the monitoring wave receiving element, the ultrasonic wave is formed in a cylindrical shape by passing the ultrasonic wave from the monitoring sound source unit through the internal space. The fire detector according to any one of claims 1 to 6, further comprising a cylindrical body that narrows a diffusion range.   The cylindrical body has an internal space divided into the monitoring space and the reference space by a partition wall along a longitudinal direction, and the suspended space includes smoke particles that communicate the monitoring space and the external space on the monitoring space side. The monitoring receiving element and the reference receiving element are arranged in each of the monitoring space and the reference space on one end surface in the longitudinal direction of the cylindrical body, The monitoring sound source unit and the reference sound source unit include a single sound wave generating element disposed on the other end surface in the longitudinal direction of the cylindrical body so as to straddle the monitoring space and the reference space. The fire detector according to claim 7.   The reference space is surrounded by a blocking wall that blocks floating particles including smoke particles, and the blocking wall has micropores having a size that prevents the floating particles from passing therethrough, and the reference space and the external space are formed by the microholes. The fire detector according to any one of claims 1 to 8, wherein

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