JP4816525B2 - 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. 16, 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, as shown in FIG. 17, the sound pressure of the ultrasonic waves from the monitoring sound source unit 1 decreases before reaching the monitoring receiving element 3, and the output of the monitoring receiving element 3 is attenuated. Since the amount increases approximately in proportion to the smoke concentration in the monitoring space, the presence or absence of a fire can be determined by estimating the smoke concentration based on this attenuation amount.

  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.

  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 cut off, the control unit that controls the monitoring sound source unit and the reference sound source unit The monitoring receiving element, the reference receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the reference sound source unit, and the outputs of the monitoring receiving element and the reference receiving element have the same frequency and the same phase. A signal processing unit for determining the presence or absence of a fire based on a differential output corresponding to a difference between outputs of the monitoring receiving element and the reference receiving element when the control unit synchronizes and controls the monitoring sound source unit and the reference sound source unit; The signal processing unit includes a change from an initial value of the differential output. Smoke density estimating means for estimating the smoke density of the monitoring space based on the amount, smoke type judging means for judging the presence or absence of a fire by comparing the smoke density estimated by the smoke density estimating means with a predetermined threshold value; It is characterized by having.

  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 ultrasonic waves to the blocked reference space, a monitoring receiving element for detecting the sound pressure of the ultrasonic waves transmitted from the monitoring sound source unit, and a wave transmitted from the reference sound source unit The control unit synchronizes the monitoring sound source unit and the reference sound source unit so that the output of the reference receiving element for detecting the sound pressure of the ultrasonic wave and the monitoring receiving element and the reference receiving element have the same frequency and the same phase. A signal processing unit that determines the presence or absence of a fire based on a differential output corresponding to the difference between the output of the monitoring receiving element and the reference receiving element when the Based on the amount of change from the initial value, the smoke density in the monitoring space Therefore, the sound pressure of the ultrasonic wave transmitted from the monitoring sound source changes according to the change in the surrounding environment of the fire detector, or the ultrasonic wave when propagating through the medium air even if the smoke concentration is constant Even if the attenuation factor of the monitor changes or the sensitivity of the monitor receiving element changes, the output fluctuation of the monitor receiving element due to these changes does not affect the differential output, and the result In particular, the accuracy of smoke density estimation in the monitoring space is improved, and non-fire reports and misreports can be reduced.

  According to a second aspect of the present invention, in the first aspect of the invention, the monitoring sound source unit and the reference sound source unit can transmit a plurality of types of ultrasonic waves having different frequencies from each other, and the signal processing unit includes: Storage means for storing relational data between the output frequency of the monitoring sound source unit and the amount of change from the initial value of the differential output according to the type and smoke concentration of airborne particles present in the monitoring space, from the monitoring sound source unit Particle type estimation means for estimating the type of particles floating in the monitoring space using the differential output for each ultrasonic wave transmitted at each frequency and the relational data stored in the storage means. The smoke concentration estimating means is configured to detect smoke in the monitoring space based on a change amount from an initial value of the differential output with respect to an ultrasonic wave having a specific frequency when the particles estimated by the particle type estimating means are smoke particles. Characterized by estimating concentration To.

  According to this configuration, in the signal processing unit, in the particle type estimation unit, monitoring is performed using the differential output 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 space is estimated, and when the particles estimated by the particle type estimation means are smoke particles, the smoke density estimation means uses the differential output from the initial value for the ultrasonic wave of a specific frequency. Since the smoke concentration in the monitoring space is estimated based on the amount of change, it is possible to identify, for example, smoke particles and steam by estimating the type of particles floating in the monitoring space in the particle type identification means. Compared to the light smoke detector and the light-reduced smoke detector, it is possible to reduce non-fire reports due to steam, and it is also suitable for use in kitchens and bathrooms.

  According to a third aspect of the present invention, in the second aspect of the present invention, the storage means outputs, as the relation data, an output frequency of the sound source unit and an amount of change from an initial value of the differential output as an output of the reference receiving element. It stores the relationship data with the rate of change divided.

  According to the present invention, even when the output of the reference receiving element fluctuates according to the output frequency of the sound source unit, the influence of fluctuations in the output frequency of the sound source unit and the output of the reference receiving element is eliminated. By using the relationship data with the rate of change, it is possible to estimate the type of particles floating in the monitoring space without being affected by fluctuations in the output of the reference receiving element.

  The invention of claim 4 is the invention of claim 2 or claim 3, wherein the monitoring sound source unit and the reference sound source unit are each composed of a single sound wave generating element capable of transmitting the plurality of types of ultrasonic waves, The control unit controls the monitoring sound source unit and the reference sound source unit so that a plurality of types of ultrasonic waves are sequentially transmitted from each sound wave generating element.

  According to this configuration, compared with the case where each of the monitoring sound source unit and the reference sound source unit includes a plurality of sound wave generating elements capable of transmitting various ultrasonic waves, the monitoring sound source unit and the reference sound source unit are reduced in size, Cost reduction is possible.

  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.

  According to a sixth aspect of the invention, in the fifth aspect of the invention, 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.

  The invention according to claim 7 is the invention according to any one of claims 1 to 6, wherein the monitoring space and the reference space are adjacent to each other with a partition wall therebetween, and the monitoring receiving element and the reference receiving element And a pressure receiving portion that receives sound pressure on each of the monitoring space side and the reference space side, and the control unit synchronizes the monitoring sound source unit and the reference sound source unit. It is characterized by comprising a single differential wave receiving element that detects the difference between the sound pressures received by both pressure receiving portions as the differential output when controlled.

  According to this configuration, since the monitoring receiving element and the reference receiving element are composed of a single differential receiving element, the monitoring receiving element and the reference receiving element are provided separately, and the difference between the outputs of both is received. As in the case of differential output, noise generated individually by the monitoring receiving element and the reference receiving element is not superimposed on the differential output, and therefore, noise included in the differential output can be reduced. And the SN ratio is improved.

  The invention according to claim 8 is the invention according to claim 7, wherein the signal processing unit controls the reference sound source unit by the control unit and transmits ultrasonic waves only from the reference sound source unit. It has an output correcting means for measuring the output of the type receiving element as a reference value and correcting the differential output based on the amount of change from the initial value of the reference value.

  According to this configuration, the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit and the reference sound source unit or the differential type receiving wave according to the change over time of the monitoring sound source unit and the reference sound source unit or the differential receiving element. Even if the sensitivity of the element may change, fluctuations in the amount of change from the initial value of the differential output due to these changes can be removed by correction by the output correction means, and long-term reliability is ensured. Get higher.

  The invention according to claim 9 is the sound according to the invention according to claim 7 or 8, wherein the differential wave receiving element has a fixed electrode and a movable electrode that are arranged to face each other, and is received by the two pressure receiving portions. It is characterized by comprising a capacitance type microphone in which the distance between the fixed electrode and the movable electrode changes according to the pressure difference and the capacitance between the fixed electrode and the movable electrode changes.

  According to this configuration, since the differential wave receiving element is formed of a capacitance type microphone, it has an advantage that it has a flat frequency characteristic and a reverberation component generation period in the output is short.

  According to a tenth aspect of the present invention, in any one of the first to ninth aspects, 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 is characterized by having fine holes of a size that is not allowed to be communicated with the reference space and the external space.

  According to this configuration, since the reference space and the external space are communicated with each other by a micropore having a size that does not allow airborne particles including smoke particles to pass therethrough, fire detection is performed while blocking the entry of airborne particles into the reference space. Changes such as humidity and atmospheric pressure in the surrounding environment of the vessel are also reflected in the reference space through the fine holes, and the influence of output fluctuations of the monitoring receiving element caused by these changes can be removed from the differential output, Non-fire reports and missed reports can be reduced.

  In the present invention, the smoke density estimation means estimates the smoke density in the monitoring space based on the amount of change from the initial value of the differential output, so that it is sent from the monitoring sound source unit according to the change in the surrounding environment of the fire detector. The sound pressure of the ultrasonic wave to be changed may change, the attenuation factor of the ultrasonic wave when propagating through the medium air even if the smoke concentration is constant, or the sensitivity of the monitoring receiving element may change. Even if this occurs, fluctuations in the output of the monitoring receiving element due to these changes will not affect the differential output, and as a result, the accuracy of smoke concentration estimation in the monitoring space will be improved, and non-fire reports and loss will occur. There is an effect that information can be reduced.

(Embodiment 1)
As shown in FIG. 1, the fire detector of 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. Based on the output of the reference receiving element 30, the difference between the outputs of the monitoring receiving element 3 and the reference receiving element 30, and amplifying and outputting the difference, the presence or absence of a fire is determined based on the output of the differential amplifying part 7. And a signal processing unit 4 for determination.

  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 opposite to each other on one surface side of the circuit board 5, and the control unit 2, the differential amplification unit 7, and the signal processing unit 4 are provided on the circuit board 5. It has been. A cylindrical body 81 is disposed between the monitoring sound source unit 1 and the monitoring wave receiving element 3, and is formed in a cylindrical shape between the reference sound source unit 10 and the reference wave receiving element 30. A cylindrical body 82 is provided. Each of the cylinders 81 and 82 is a straight tubular square tube, and one end surface in the longitudinal direction (left end surface in FIG. 2) is closed by each of the monitoring sound source unit 1 and the reference sound source unit 10 and the other end surface. 2 (the right end surface in FIG. 2) is closed by each of the monitoring receiving element 3 and the reference receiving element 30, and ultrasonic waves from each of the monitoring sound source unit 1 and the reference sound source unit 10 are propagated through the internal space. Therefore, the ultrasonic waves transmitted from each of the monitoring sound source unit 1 and the reference sound source unit 10 are prevented from diffusing by passing through the internal spaces of the cylinders 81 and 82, and the decrease in sound pressure due to the diffusion of the ultrasonic waves is suppressed. can do. The cylindrical body 81 functions as a sound insulation wall 6 (see FIG. 16) that is provided around the monitoring receiving element 3 and prevents the ultrasonic waves generated from other than the monitoring sound source unit 1 from entering the monitoring receiving element 3. Doubles as

  Here, the cylinder 81 has a plurality of communication holes 81a having a size through which suspended particles including smoke particles pass on the side surface along the longitudinal direction, whereby the monitoring sound source unit 1 and the monitoring receiving element 3 are connected to each other. In the meantime, a monitoring space Sp1 is formed which communicates with the external space (outside air) around the fire detector through the communication hole 81a in order to monitor the presence or absence of a fire. On the other hand, the cylindrical body 82 also functions as a blocking wall that blocks floating particles including at least smoke particles. Intrusion of floating particles is blocked between the reference sound source unit 10 and the reference receiving element 30. A reference space Sp2 is formed. 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. Furthermore, in this embodiment, the length dimension and opening shape of both the cylinders 81 and 82 are set to be the same, and the shapes of the monitoring space Sp1 and the reference space Sp2 are substantially the same. In addition, since the invasion of suspended particles is blocked in the reference space Sp2, the temperature of the reference space Sp2 is the same as that of the external space (outside air) and the monitoring space Sp1, but there are smoke particles and steam in the reference space Sp2. There is no invasion. Here, in the present embodiment, the cylindrical body 82 has a filter (for example, a porous ceramic filter) in which a large number of micropores (not shown) having a size that does not allow airborne particles to pass therethrough is formed. Sp2 communicates with the external space. 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.

  In the present 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 an ultrasonic wave having a short time is 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. In the following, 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. 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.

  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.

  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. The control unit 2 controls the monitoring sound source unit 1 and the reference sound source unit 10 in synchronization so that the ultrasonic waves transmitted from the monitoring sound source unit 1 and the reference sound source unit 10 have the same frequency and the same phase. The monitoring sound source unit 1 and the reference sound source unit 10 are controlled in two types of operation modes: a synchronous mode and an asynchronous mode in which ultrasonic waves are transmitted from only one of the monitoring sound source unit 1 and the reference sound source unit 10. In the present embodiment, the monitoring sound source unit 1 and the reference sound source unit 10 are driven under the same conditions (for example, the sound pressure of ultrasonic waves to be transmitted), and the monitoring wave receiving element 3 and the reference wave receiving element 30 are the same. In addition, 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. When the control unit 2 controls the monitoring sound source unit 1 and the reference sound source unit 10 in the synchronous mode, there is no invasion of suspended particles in 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 of the monitoring receiving element 3 and the output of the reference receiving element 30 are the same not only in frequency and phase but also in intensity.

  The differential amplifying unit 7 takes the difference between the outputs of the monitoring receiving element 3 and the reference receiving element 30, further amplifies the difference, and outputs the difference. The output of the differential amplifying unit 7 when the reference sound source unit 10 is controlled is hereinafter referred to as a differential output. That is, when the control unit 2 controls the monitoring sound source unit 1 and the reference sound source unit 10 in synchronization so that the outputs of the monitoring wave receiving element 3 and the reference wave receiving element 30 have the same frequency and the same phase. This corresponds to the difference between the outputs of the monitoring receiving element 3 and the reference receiving element 30. Therefore, as described above, if there is no invasion of suspended particles in 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 differential output becomes zero. Therefore, in this embodiment, the initial value of the differential output is set to zero.

  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 amount of change from the initial value of the differential output described above. 41, the smoke type judgment means 42 for judging the presence or absence of a fire by comparing the smoke density estimated by the smoke density estimation means 41 with a predetermined threshold, and the monitoring sound source unit 1 after transmitting the ultrasonic wave The sound speed detecting means 43 for obtaining the sound speed based on the time difference until the ultrasonic wave is received by the monitoring wave receiving element 3, and the temperature for estimating the temperature of the monitoring space Sp1 based on the sound speed obtained by the sound speed detecting means 43 An estimation unit 44 and a thermal type determination unit 45 that compares the temperature estimated by the temperature estimation unit 44 with a specified temperature to determine the presence or absence of a fire are provided. The signal processing unit 4 is configured by a microcomputer, and each of the means 41 to 45 is realized by mounting an appropriate program on the microcomputer. The signal processing unit 4 is provided with an A / D converter that performs analog-digital conversion on the output signal of the differential amplification unit 7.

  The smoke density estimation means 41 is the amount of change from the initial value (zero) of the differential output that is the output of the differential amplifier 7 when the control unit 2 controls the monitoring sound source unit 1 and the reference sound source unit 10 in the synchronous mode. The smoke amount is estimated based on the above, but if the frequency of the ultrasonic wave transmitted from the monitoring sound source unit 1 and the reference sound source unit 10 is constant, the amount of change is approximately equal to the smoke concentration in the monitoring space Sp1. Increase proportionally. That is, the attenuation amount of the output of the monitoring receiving element 3 that receives the ultrasonic wave from the monitoring sound source unit 1 through the monitoring space Sp1 increases in proportion to the smoke concentration in the monitoring space Sp1, but the invasion of suspended particles is blocked. Since the output of the reference receiving element 30 that receives the ultrasonic wave from the reference sound source unit 10 through the reference space Sp2 is not changed depending on the smoke density in the monitoring space Sp1, the monitoring receiving element 3 and the reference receiving element 30 The amount of change in the differential output corresponding to the output difference increases substantially in proportion to the smoke density in the monitoring space Sp1. Therefore, if the relational expression between the smoke density and the amount of change is calculated and stored based on the relationship data between the smoke density measured in advance and the amount of change in the differential output, the change in the differential output using the above relational expression is stored. The smoke concentration can be estimated from the quantity. 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 transmits the alarm sound composed of audible sound waves from the monitoring sound source unit 1 to the monitoring sound source unit 1 in the asynchronous mode. Control the drive input waveform. 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. In addition, the sound velocity detection means 43 controls the monitoring sound source unit 1 in the asynchronous mode and controls the monitoring sound source unit 1 in an asynchronous mode separately from the ultrasonic wave transmitted from the monitoring sound source unit 1 to estimate the smoke density. The sound source may be periodically transmitted from the monitoring sound source unit 1 and the sound speed may be obtained based on the time difference until the ultrasonic wave is received by the monitoring wave receiving element 3, or the control unit may be used to estimate the smoke density. 2 may control the monitoring sound source unit 1 and the reference sound source unit 10 in the synchronous mode, and obtain the sound velocity using ultrasonic waves transmitted from the monitoring sound source unit 1. The sound speed may be obtained based on the 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.

  Hereinafter, the operation of the fire detector of the present embodiment will be described with reference to FIG. The control unit 2 periodically transmits ultrasonic waves simultaneously from the monitoring sound source unit 1 and the reference sound source unit 10 by controlling the monitoring sound source unit 1 and the reference sound source unit 10 in the synchronous mode. Here, if there is no smoke in the monitoring space Sp1 (that is, FIG. 5 (e) is “No”), the output of the reference receiving element 10 shown in FIG. 5 (a) and the monitoring receiving wave shown in FIG. 5 (b). The output of the element 1 is the same, and the difference between the two becomes zero as shown in FIG. Therefore, the differential output of FIG. 5D, which is the output of the differential amplifier 7 that amplifies the difference of FIG. 5C, is zero (initial value). Here, the smoke density estimation means 41 estimates the smoke density of the monitoring space Sp1 based on the change amount from the initial value of the differential output, but the change amount from the initial value of the differential output is zero. When the estimated smoke density is less than the threshold value, the smoke type determination means 42 determines that “no fire”.

  On the other hand, if smoke is present in the monitoring space Sp1 (that is, FIG. 5 (e) is “present”), the output of the reference receiving element 10 shown in FIG. 5 (a) does not change, but FIG. The output of the monitoring receiving element 1 shown is attenuated according to the smoke density in the monitoring space Sp1, and a difference occurs between them as shown in FIG. Therefore, the differential output, which is the output of the differential amplifier 7 that amplifies the difference in FIG. 5C, changes from zero (initial value). The amount of change from the initial value of the differential output at this time increases approximately in proportion to the smoke density in the monitoring space Sp1. Here, the smoke density estimation means 41 estimates the smoke density in the monitoring space Sp1 based on the amount of change from the initial value of the differential output, and the smoke type judgment means 42 determines the smoke estimated by the smoke density estimation means 41. If the concentration is equal to or higher than the above threshold, it is determined that there is a fire.

  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 are driven under the same conditions (for example, the sound pressure of ultrasonic waves to be transmitted), and the monitoring receiving element 3 and the reference receiving element 30 Are used under the same conditions (for example, DC bias voltage), the monitoring sound source unit 1 and the reference sound source unit 10 are driven under different conditions, and the monitoring wave receiving element 3 and the reference wave receiving element 30 are May be used under different conditions. In this case, when the monitoring space Sp1 and the reference space Sp2 are in the same state (for example, temperature, humidity, atmospheric pressure) without the invasion of suspended particles in the monitoring space Sp1, the monitoring sound source unit 1 and the reference sound source unit 10 Even if ultrasonic waves with the same frequency and the same phase are transmitted, the differential output does not become zero, but if the differential output at this time is the initial value, it is based on the amount of change in the differential output from the initial value. Thus, the smoke density in the monitoring space Sp1 can be estimated.

  In the fire detector according to the present embodiment described above, the smoke density estimating means 41 has the monitoring space Sp1 between the monitoring sound source unit 1 and the monitoring receiving element 3 based on the amount of change from the initial value of the differential output. The smoke density 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. A photoelectric fire detector such as a light smoke detector can eliminate the influence of background light, which is a problem, and can eliminate the labyrinth required for the scattered light smoke detector, resulting in a fire. Occasionally, smoke particles are likely to diffuse into the monitoring space Sp1, so that the responsiveness can be improved as compared with the scattered light type smoke detector, and the non-fire report can be reduced as compared with the reduced light type smoke detector.

  In the fire detector having the above-described configuration, the sound pressure of the ultrasonic wave transmitted from the monitoring sound source unit 1 changes in accordance with changes in the surrounding environment (for example, changes in temperature, humidity, atmospheric pressure, etc.). Or even if the smoke concentration is constant, the attenuation rate of the ultrasonic wave when propagating through the air as the medium changes, or the sensitivity of the monitoring receiving element 3 changes, so that the smoke concentration in the monitoring space Sp1 changes. Regardless, the output of the monitoring receiving element 3 may change. However, since the output fluctuation equivalent to the output fluctuation of the monitoring receiving element 3 at this time also occurs in the output of the reference receiving element 30, the difference between the outputs of the monitoring receiving element 3 and the reference receiving element 30 is caused. In the corresponding differential output, the output fluctuation of the monitoring receiving element 3 and the output fluctuation of the reference receiving element 30 are canceled out, so that the influence of these output fluctuations is eliminated. Therefore, in the fire detector of the present embodiment that estimates the smoke concentration in the monitoring space Sp1 based on the amount of change from the initial value of the differential output instead of the output of the monitoring receiving element 3 alone, there is a change in the surrounding environment. However, the smoke concentration in the monitoring space Sp1 can be estimated without being affected by this change, and as a result, the accuracy of the smoke concentration estimation in the monitoring space Sp1 is improved, and non-fire reports and misreports are 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 fire detector of the present embodiment has a basic configuration substantially the same as that of the first embodiment, and the monitoring receiving element 3 and the reference receiving element 30 described in the first embodiment are a single unit as shown in FIG. The point which consists of the differential type | mold receiving element 9 differs from the fire detector of Embodiment 1. FIG. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  In the present embodiment, as shown in FIG. 7, a cylinder 81 that forms the monitoring space Sp1 and a cylinder 82 that forms the reference space Sp2 are stacked in the thickness direction of the circuit board 5 (see FIG. 2). Yes. As a result, the monitoring space Sp1 and the reference space Sp2 are adjacent to each other with the side walls of the cylinder 81 and the cylinder 82 facing each other as the partition walls. The side walls of the cylinder 81 and the cylinder 82 serving as the partition walls may be integrated. Here, the end surface opposite to the monitoring sound source unit 1 in the longitudinal direction of the cylinder 81 and the end surface opposite to the reference sound source unit 10 in the longitudinal direction of the cylinder 82 are respectively closed.

  The differential wave receiving element 9 is disposed on a partition wall that separates the monitoring space Sp1 and the reference space Sp2 described above. In the differential wave receiving element 9, pressure receiving portions that receive sound pressure are formed on each of the monitoring space Sp <b> 1 side that is the internal space of the cylinder 81 and the reference space Sp <b> 2 side that is the internal space of the cylinder 82. The difference between the sound pressures received by the two pressure receiving portions is detected. Although not shown in FIG. 6, an amplifier that amplifies the output of the differential wave receiving element 9 is provided between the differential wave receiving element 9 and the signal processing unit 4. Here, the output of the amplifier at the subsequent stage of the differential wave receiving element 9 when the control unit 2 controls the monitoring sound source unit 1 and the reference sound source unit 10 in the synchronous mode is a differential output. That is, since the monitoring receiving element 3 and the reference receiving element 30 are made a single differential receiving element 9 in this way, it corresponds to the difference between the outputs of the monitoring receiving element 3 and the reference receiving element 30. Since the component can be directly taken out from the differential receiving element 9, as described in the first embodiment, the differential amplifying unit 7 that takes the difference between the monitoring receiving element 3 and the reference receiving element 30 (see FIG. 1). ) Is not required.

  In the present embodiment, an example in which the cylinder 81 and the cylinder 82 are stacked on the one surface side of the circuit board 5 is shown, but a single cylinder 8 is used instead of the cylinders 81 and 82. Alternatively, for example, as shown in FIG. 8, the internal space of the cylinder 8 may be divided into two equal parts into the monitoring space Sp1 and the reference space Sp2 by a partition wall 8b provided at the center in the longitudinal direction. The cylindrical body 8 has a communication hole 8a that is formed in a size that allows airborne particles including smoke particles to pass through on the monitoring space Sp1 side and communicates the inside and outside of the monitoring space Sp1, and includes the monitoring sound source unit 1, the reference sound source unit 10, and the like. Are arranged on each end face in the longitudinal direction. A portion of the cylindrical body 8 that forms the reference space Sp2 also serves as a blocking wall, 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.

  Next, a capacitive microphone is illustrated as an example of the differential receiving element 9 used in the present embodiment. As shown in FIG. 9, each of the capacitive microphones constituting the differential receiving element 9 has a pair of rectangular frames formed by providing window holes 91a penetrating in the thickness direction in the silicon substrate. A frame 91, a fixing plate 93 made of a conductive material sandwiched between the two frames 91, and a window 91a that is closed on the one surface side opposite to the fixing plate 93 of each frame 91 are formed. And a pair of movable plates 92 made of the conductive material. The fixed plate 93 has a fixed electrode 93b in the window hole 91a, and each movable plate 92 has a movable electrode 92b at a position facing the fixed electrode 93b. Here, a flexible portion 92 c that holds the movable electrode 92 b is formed around the movable electrode 92 b in the movable plate 92 so that the movable electrode 92 b can vibrate in the thickness direction of the frame 91. Further, both movable electrodes 92b are connected to each other by a connecting piece 92d made of a conductive material through a through-hole 93c provided in the fixed electrode 93b, and operate integrally. Each movable plate 92 is electrically connected to a pad 92a formed around the window hole 91a, and the fixed plate 93 is formed on the frame 91 with respect to the pad 93a formed on one surface of one frame 91. The through-hole wiring 93d is electrically connected. Although not shown in FIG. 9, the frame 91 has an insulating film at least in contact with the fixed plate 93, the movable plate 92, the pads 92a and 93a, and the through-hole wiring 93d. In the example of FIG. 9, the movable plate 92 and the fixed plate 93 are each formed from a metal thin film, but the movable plate 92 and the fixed plate 93 are not limited to a metal thin film. The flexible portion 92c may have a corrugated structure, for example.

  In the differential wave receiving element 9 composed of a capacitive microphone having the configuration shown in FIG. 9, a capacitor having the fixed electrode 93b and both movable electrodes 92b as electrodes is formed. By functioning as a pressure receiving portion and receiving the pressure of the dense wave, the distance between the fixed electrode 93b and each movable electrode 92b changes, and the capacitance between the fixed electrode 93b and each movable electrode 92b changes. Here, since both the movable electrodes 92b operate integrally, the electrostatic capacity between the fixed electrode 93b and both the movable electrodes 92b is received by the sound pressure received by one movable electrode 92b and the other movable electrode 92b. It changes according to the difference with sound pressure. Therefore, if a DC bias voltage is applied between the pad 93a electrically connected to the fixed electrode 93b and the pads 92a and 92a electrically connected to the movable electrodes 92b, the pads 92a and 92a and the pads Since a minute voltage change occurs according to the sound pressure of the ultrasonic wave between 93a, the sound pressure of the ultrasonic wave can be converted into an electric signal. Here, since both the pads 92a and 92a are electrically connected via the connecting piece 92d, the DC bias voltage may be applied between one of the pads 92a and the pad 93a. In addition, the movable piece 92b is electrically separated by forming the connecting piece 92d from an insulating material, and a change in electrostatic capacitance between the fixed electrode 93b and one of the movable electrodes 92b is measured. You may make it do.

  The differential wave receiving element 9 configured as described above has one movable plate 92 facing the monitoring space Sp1 and the other movable plate 92 facing the reference space Sp2 with respect to the partition wall separating the monitoring space Sp1 and the reference space Sp2. Is provided so that the difference between the sound pressure of the ultrasonic wave received from the monitoring sound source unit 1 in the monitoring space Sp1 and the sound pressure of the ultrasonic wave received from the reference sound source unit 10 in the reference space Sp2 is output. . According to this configuration, the differential wave receiving element 9 has an advantage that it has a flat frequency characteristic and a reverberation component generation period in the output is short.

  By the way, the signal processing unit 4 of the present embodiment is configured such that the control unit 2 controls the reference sound source unit 10 in the asynchronous mode and transmits the ultrasonic wave only from the reference sound source unit 10. Is output as a reference value, and output correction means (not shown) for correcting the differential output based on the amount of change from the initial value of the reference value. That is, the output correction means receives the reference value from the differential wave receiving element 9, holds a correction coefficient based on the rate of change of the reference value from the initial value, and corrects the differential output corrected using this correction coefficient. Is output to the smoke density estimating means 41 in the subsequent stage. Here, the initial value of the reference value is a reference value detected when no change with time (for example, aging deterioration) has occurred in the fire detector (for example, before shipment), and is stored in advance in the output correction means. The 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 every time before the monitoring sound source unit 1 and the reference sound source unit 10 are driven to detect the smoke density in the monitoring space Sp1, and the reference value is obtained. It is configured to measure and calculate a correction coefficient. Therefore, the correction coefficient is updated each time the smoke density is detected in the monitoring space Sp1.

  Here, the rate of change from the initial value of the reference value is determined according to changes over time (for example, aging degradation) of the monitoring sound source unit 1, the reference sound source unit 10, and the differential wave receiving element 9, and this rate of change. If the differential output is corrected using the correction coefficient based on the above, a differential output excluding the influence of the change with time can be obtained. Therefore, in the amount of change from the initial value of the corrected differential output used in the smoke density estimation means 41, the influence of the change with time is removed, and the accuracy of smoke density estimation in the monitoring space Sp1 is improved.

  Below, the operation example of the fire detector of this embodiment is demonstrated on the basis of the flowchart of FIG. First, for example, before shipment of the fire detector, the reference sound source unit 10 is driven in the asynchronous mode to acquire the initial value of the reference value, and the initial value is held in the output correcting means (step S1). Then, after the fire detector is installed, the reference sound source unit 10 is driven in the asynchronous mode and the reference value is measured before the monitoring sound source unit 1 and the reference sound source unit 10 are driven in the synchronous mode. A correction coefficient is calculated based on the rate of change from (step S2). Thereafter, the monitoring sound source unit 1 and the reference sound source unit 10 are simultaneously driven in a synchronous mode to obtain a differential output, and the differential output is corrected by using the correction coefficient in the output correction means, thereby obtaining a differential output. The influence of the change with time is removed from (step S3). Then, using the corrected differential output, the smoke density estimating means 41 estimates the smoke density in the monitoring space Sp1, 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.

Here, for example, when it is assumed that the sensitivity decrease of an amount of Msens (0 ≦ Msens ≦ 1) has occurred in the differential receiving element 9 due to a change with time, when ultrasonic waves are transmitted only from the reference sound source unit 10 Output of the differential type receiving element 9 (that is, the reference value) is Pref, the initial value of Pref is Pref0, and the output of the differential type receiving element 9 when ultrasonic waves are transmitted only from the monitoring sound source unit 1 Is Pmes and the initial value of Pmes is Pmes0, the output correction means
Pref = (1−Msens) × Pref0
The correction coefficient (1-Msens) can be calculated from the equation of
Pmes0-Pref0 = (1 / (1-Msens)) * (Pmes-Pref)
Thus, the differential output (Pmes-Pref) can be corrected.

  In the present embodiment, an example is shown in which the ultrasonic wave is transmitted only from the reference sound source unit 10 to measure the reference value and the correction coefficient is calculated before estimating the smoke density of the monitoring space Sp1. The configuration may be such that the correction coefficient is calculated once every time the smoke density of Sp1 is estimated a plurality of times. For example, in an environment where the correction coefficient is less likely to fluctuate, the frequency of correction coefficient calculation (that is, updating) is set. It is also possible to reduce power consumption by reducing the number.

  In the fire detector of the present embodiment described above, the differential output is periodically corrected by the output correction means, whereby the monitoring sound source unit 1, the reference sound source unit 10, and the differential receiving element 9 change with time ( For example, it is possible to eliminate the fluctuation of the differential output corresponding to the aging deterioration, and the long-term reliability is improved. Further, as described in the first embodiment, when the monitoring receiving element 3 and the reference receiving element 30 are separately provided and the difference between both outputs is taken by the differential amplifying unit 7 and the difference output is obtained, the monitoring receiving element is received. Although noise generated individually by the wave element 3 and the reference wave receiving element 30 may be superimposed on the differential output, in this embodiment, the monitoring wave receiving element 3 and the reference wave receiving element 30 are combined into a single Since the differential wave receiving element 9 is used, it is possible to reduce noise included in the differential output and to improve the SN ratio.

(Embodiment 3)
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. Here, the attenuation amount (I ₀ −I _x ) of the sound pressure I _x received by the monitoring receiving element 3 in the state where suspended particles exist in the monitoring space Sp1 with respect to the reference sound pressure I ₀ is the difference described above. Since this corresponds to the amount of change from the initial value of the dynamic output, the sound pressure attenuation rate represented by (I ₀ −I _x ) / I ₀ is the amount of change from the initial value of the differential output as the reference receiving element. divided by the (corresponding to the reference sound pressure I ₀₎ output 30 (hereinafter referred to as the rate of change of the differential output) corresponding to. In particular, the rate of change of the differential output corresponding to the unit attenuation rate is defined as the unit rate of change, and the result of normalizing the unit rate of change of each output frequency with the unit rate of change when the output frequency is 82 kHz as 1. The unit change rate.

  Based on the above-described knowledge, in the present embodiment, the control sound source unit 1 causes the control unit 2 to sequentially transmit a plurality of types of ultrasonic waves having different frequencies from the monitor sound source unit 1 and the reference sound source unit 10. The reference sound source unit 10 is controlled in a synchronous mode, and the signal processing unit 4 is configured to monitor the sound source unit according to at least the output of the reference wave receiving element 30, the type of suspended particles present in the monitored space Sp1, and the suspended particle concentration 1 data related to the output frequency of 1 and the relative unit change rate of the differential output (corresponding to the relative unit attenuation rate of the output of the monitoring receiving element 3) (equivalent to the data extracted from FIG. 13 above), smoke A storage means 48 storing a unit change rate of differential output (corresponding to data extracted from FIG. 12 described above) at a specific frequency (for example, 82 kHz) with respect to particles, and each frequency transmitted from the monitoring sound source unit 1 Super A particle type estimation unit 46 for estimating the type of particles floating in the monitoring space Sp1 using the differential output for each wave and the relational data stored in the storage unit 48, and a particle type estimation unit 46 Smoke density estimating means 47 for estimating the smoke density in the monitoring space Sp1 based on the amount of change from the initial value of the differential output for an ultrasonic wave of a specific frequency (for example, 82 kHz) when the estimated particle is a smoke particle; The smoke density estimation means 47 comprises a smoke type judgment means 42 for judging the presence or absence of a fire by comparing the smoke density estimated by the smoke density estimation means 47 with a predetermined threshold value.

  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 each of the monitoring sound source unit 1 and the reference sound source unit 10, and a differential output corresponding to a difference between outputs of the monitoring wave receiving element 3 and the reference wave receiving element 30 for each ultrasonic wave. Is measured by the signal processing unit 4 (step S11). The particle type estimation means 46 obtains the rate of change of the differential output from the differential output and the output of the reference receiving element 30 stored in the storage means 48 for each output frequency (step S12), and the output frequency is 82 kHz. The ratio of the change rate of the differential output at 20 kHz to the change rate of the differential output at is calculated (step S13). The storage means 48 stores the relative unit change rate at 20 kHz with respect to the relative unit change 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 change rate of the differential output. (In the case of FIG. 13, the white smoke is 0, the black smoke is 0.2, and the steam is 0.5), and the particle type estimation means 46 calculates the change rate of the calculated differential output. The ratio is compared with the relationship data stored in the storage means 48, and the type of particle having the closest ratio of change rate in the relationship 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 sound pressure attenuation rate (corresponding to the change rate of the differential output) is shown by a straight line. The smoke concentration estimation means 47 stores the change rate of the differential output with respect to the ultrasonic wave of a specific frequency (for example, 82 kHz) for the estimated particle type. 48, the ratio of the differential output to the unit change rate is calculated. When the value of the ratio is y, the smoke density in the monitoring space Sp1 is the smoke density y% / It is estimated that it corresponds to m (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 rate of change when the output frequency is 82 kHz and the rate of change when the output frequency is 20 kHz. However, the present invention is not limited to the combination of these output frequencies. An output frequency may be used. Furthermore, the rate of change 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 particle type estimation means 46, the smoke concentration estimation means 47, and the smoke type determination means 42 are realized by mounting an appropriate program on the microcomputer. Yes. The signal processing unit 4 is provided with an A / D converter that performs analog-digital conversion on the output signal of the differential amplification unit 7.

  Here, each of the monitoring sound source unit 1 and the reference sound source unit 10 uses one of the sound wave generating elements described in the first embodiment, and the control unit 2 described above includes the monitoring sound source unit 1 and the reference sound source unit. By sequentially changing the frequency of the drive input waveform applied to the unit 10, plural types of ultrasonic waves having different frequencies are sequentially transmitted from the monitoring sound source unit 1 and the reference sound source unit 10. 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). In addition, the frequency of the ultrasonic wave transmitted from the reference sound source unit 10 is changed from the lower limit frequency (for example, 20 kHz) to the upper limit frequency (for example, 82 kHz) in synchronization with the ultrasonic wave transmitted from the monitoring sound source unit 1. In this embodiment, the control unit 2 controls the monitoring sound source unit 1 and the reference sound source unit 10 so that four 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. Although it is configured to control, the frequency of the ultrasonic waves transmitted from the monitoring sound source unit 1 and the reference sound source unit 10 is not limited to four types, and may be a plurality of types. Compared with the case where the above ultrasonic waves are sequentially transmitted, the burden on the control unit 2 and the signal processing unit 4 can be reduced, and the control unit 2 and the signal processing unit 4 can be simplified. In this embodiment, by using the sound wave generating element described in the first embodiment for each of the monitoring sound source unit 1 and the reference sound source unit 10 as described above, the ultrasonic waves sequentially transmitted are ultrasonic waves having different frequencies. Therefore, it is possible to reduce the cost compared to the case where a plurality of piezoelectric elements having different resonance frequencies are used for each of the monitoring sound source unit 1 and the reference sound source unit 10 and continuous wave ultrasonic waves are transmitted from each piezoelectric element. I can plan.

  In the present embodiment, the relationship data between the output frequency of the monitoring sound source unit 1 and the relative unit change rate of the differential output is stored in the storage unit 48. However, suspended particles that exist in the monitoring space Sp1 in the first place. Since it is the amount of change from the initial value of the differential output that changes for each output frequency of the monitoring sound source unit 1 according to the type of the above, the relational data stored in the storage means 48 is the output frequency of the monitoring sound source unit 1 And the amount of change from the initial value of the differential output may be data, and instead of the above-described relative unit change rate, for example, the amount of change from the initial value of the differential output or the differential output The change rate obtained by dividing the change amount from the initial value by the output of the reference receiving element 30 or the relation data adopting the unit change rate may be stored in the storage means 48.

  In the fire detector of the present embodiment described above, in the particle type estimation unit 46, the differential output for each ultrasonic wave transmitted from the monitoring sound source unit 1 and the relationship data stored in 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 based on the amount of change from the initial value of the differential output, and the smoke type judging means 42 compares the smoke density estimated by the smoke density estimating means 47 with a predetermined threshold value. Therefore, it is possible to eliminate the influence of background light, which is a problem with photoelectric fire detectors such as scattered light type smoke detectors and dimming type smoke detectors. Rabbi required for smoke detectors Compared to light scattering type smoke detector to be able to eliminate the Nsu body can improve the response and the reduction of non-fire report is made possible as compared with the dimming smoke sensor. 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 applies 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 the monitoring sound source is composed of a plurality of sound wave generating elements having different output frequencies. The unit 1 and the reference sound source unit 10 may be configured respectively. In this case, an element that generates ultrasonic waves by mechanical vibration, such as a piezoelectric element, is used as each sound wave generating element, and each sound wave generating element is driven at the respective resonance frequency, whereby the monitoring sound source unit 1 and the reference sound source The sound pressure of the ultrasonic wave transmitted from each of the units 10 can be increased to contribute to the improvement of the SN ratio. In addition to sequentially driving each sound wave generating element to send multiple types of ultrasonic waves, it is also possible to simultaneously drive multiple sound wave generating elements to send multiple types of ultrasonic waves simultaneously Become.

  Further, an individual monitoring receiving element 3 and a reference receiving element 30 may be provided for each sound wave generating element. In this case, each of the monitoring receiving element 3 and the reference receiving element 30 is provided. By using a piezoelectric element or the like having a relatively large Q value of the resonance characteristics, and using each of the monitoring receiving elements 3 and each of the reference receiving elements 30 for receiving ultrasonic waves of the respective resonance frequencies, the monitoring receiving elements 3 and The sensitivity of the reference receiving element 30 can be improved. Furthermore, if a plurality of sound wave generating elements 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 simultaneously, and the monitoring space Sp1 can be detected in a short period. It is possible to accurately estimate the type of suspended particles and the smoke concentration by detecting the attenuation of sound pressure for a plurality of types of ultrasonic waves without being affected by a general change with time (for example, the concentration change of suspended particles). Further, it is also conceivable that the sound wave generating element constituting the monitoring sound source unit 1 is also used as the monitoring wave receiving element 3, and the sound wave generating element constituting the reference sound source unit 10 is also used as the reference wave receiving element 30, in this case, Although a reflecting surface for reflecting the ultrasonic wave transmitted from each sound wave generating element toward the sound wave generating element is required, the cost can be reduced by reducing the number of elements.

  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 has an insecticidal effect by controlling the monitoring sound source unit 1 in the asynchronous mode separately from the ultrasonic wave having a frequency transmitted from the monitoring sound source unit 1 in order to estimate the smoke density. An ultrasonic wave with a frequency may be transmitted periodically, or the control unit 2 controls the monitoring sound source unit 1 and the reference sound source unit 10 in the synchronous mode to send smoke from the monitoring sound source unit 1 in order to estimate the smoke density. You may make it set the frequency of the ultrasonic wave made to wave to the frequency with an insect-proof 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, but, for example, a heating element associated with energization of the heating element unit using an aluminum thin 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 operation | movement explanatory drawing same as the above. It is a block diagram which shows the structure of Embodiment 2 of this invention. It is a schematic perspective view which shows the principal part same as the above. It is a schematic perspective view which shows the principal part of the other example same as the above. The differential type receiving element used for the above is shown, (a) is a schematic sectional view, and (b) is a schematic plan view. It is a flowchart which shows the operation example same as the above. 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. A prior art example is shown, (a) is a schematic bottom view, and (b) is a schematic side view. It is operation | movement explanatory drawing same as the above.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Monitoring sound source part 2 Control part 3 Monitoring receiving element 4 Signal processing part 7 Differential amplification part 8b Bulkhead 9 Differential type receiving element 10 Reference sound source part 11 Base board 12 Thermal insulation layer 13 Heating body layer (heating body part)
30 Reference wave receiving element 41 Smoke density estimation means 42 Smoke type judgment means 46 Particle type estimation means 47 Smoke density estimation means 48 Storage means 92b Movable electrode (pressure receiving part)
93b Fixed electrode Sp1 Monitoring space Sp2 Reference space

Claims (10)

  A monitoring sound source unit that communicates with the external space and can transmit ultrasonic waves to the monitoring space where smoke particles including smoke particles can enter from the external space, and a reference space where the penetration 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, The reference receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the reference sound source section, and the control section so that the outputs of the monitoring receiving element and the reference receiving element have the same frequency and the same phase. A signal processing unit that determines whether or not there is a fire based on a differential output corresponding to the difference between the output of the monitoring receiving element and the reference receiving element when the reference sound source unit is controlled in synchronization, , Based on the amount of change from the initial value of the differential output. A smoke density estimating means for estimating a smoke density in the space, and a smoke type judging means for judging the presence or absence of a fire by comparing the smoke density estimated by the smoke density estimating means with a predetermined threshold value. Fire detector.   The monitoring sound source unit and the reference sound source unit can transmit a plurality of types of ultrasonic waves having different frequencies from each other, and the signal processing unit is responsive to the type of suspended particles and smoke concentration present in the monitoring space. Storage means for storing relational data between the output frequency of the monitoring sound source section and the amount of change from the initial value of the differential output; and the differential for each ultrasonic wave transmitted from the monitoring sound source section. Particle type estimation means for estimating the type of particles floating in the monitoring space using the output and the relational data stored in the storage means, and the smoke concentration estimation means is connected to the particle type estimation means. The smoke density in the monitoring space is estimated based on a change amount from an initial value of the differential output with respect to an ultrasonic wave having a specific frequency when the estimated particle is a smoke particle. Fire detector.   The storage means stores relational data between the output frequency of the sound source unit and the rate of change obtained by dividing the amount of change from the initial value of the differential output by the output of the reference receiving element as the relational data. The fire detector according to claim 2.   Each of the monitoring sound source unit and the reference sound source unit includes a single sound wave generation element capable of transmitting the plurality of types of ultrasonic waves, and the control unit sequentially transmits a plurality of types of ultrasonic waves from each of the sound wave generation elements. 4. The fire detector according to claim 2, wherein the monitoring sound source unit and the reference sound source unit are controlled to be waved.   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 heating element unit and the base substrate on the one surface side of the base substrate, while the heating element 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.   The monitoring space and the reference space are adjacent to each other with a partition wall therebetween, and the monitoring wave receiving element and the reference wave receiving element are disposed on the partition wall and are provided between the monitoring space side and the reference space side. A pressure receiving part for receiving sound pressure is formed on each of them, and a difference between sound pressures received by both pressure receiving parts when the control unit controls the monitoring sound source part and the reference sound source part in synchronization with each other. The fire detector according to any one of claims 1 to 6, wherein the fire detector is a single differential type receiving element.   The signal processing unit controls the reference sound source unit with the control unit and measures the output of the differential receiving element in a state where ultrasonic waves are transmitted only from the reference sound source unit as a reference value. 8. The fire detector according to claim 7, further comprising output correcting means for correcting the differential output based on a change amount from an initial value of a reference value.   The differential wave receiving element has a fixed electrode and a movable electrode arranged to face each other, and a distance between the fixed electrode and the movable electrode changes according to a difference in sound pressure received by the two pressure receiving portions. The fire detector according to claim 7 or 8, comprising a capacitance type microphone in which a capacitance between the fixed electrode and the movable electrode changes.   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 does not allow the floating particles to pass through, and the reference space and the external space are formed by the microholes. The fire detector according to any one of claims 1 to 9, wherein

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