JP4950709B2 - 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 present applicant has proposed a fire detector that detects the presence or absence of smoke using ultrasonic waves (see FIG. 2).

  The fire detector includes a sound source unit 1 capable of transmitting ultrasonic waves, a control unit 2 that controls the sound source unit 1, a wave receiving element 3 that detects sound pressure of ultrasonic waves transmitted from the sound source unit 1, And a signal processing unit 4 for determining the presence or absence of a fire based on the output of the wave receiving element 3. The signal processing unit 4 includes smoke concentration estimation means 41 that estimates the smoke concentration in the monitoring space between the sound source unit 1 and the wave receiving element 3 based on the attenuation amount from the reference value of the output of the wave receiving element 3, and the estimation A smoke type judgment means 42 for judging the presence or absence of a fire by comparing the smoke concentration and a predetermined threshold value. That is, since the attenuation amount of the output of the wave receiving element 3 increases substantially 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. .

  By the way, in the ultrasonic fire detector described above, in order to maximize the amount of change in the output of the wave receiving element 3 relative to the amount of change in smoke density (that is, the amount of change in the received sound pressure at the wave receiving element 3). It is conceivable to increase the power supplied to the sound source unit 1 within a range in which the sound source unit 1 is not damaged and increase the sound pressure of the ultrasonic wave transmitted from the sound source unit 1.

  However, even if the sound pressure of the ultrasonic wave transmitted from the sound source unit 1 is increased, the ultrasonic wave diffuses between the sound source unit 1 and the wave receiving element 3, thereby determining whether smoke particles exist in the monitoring space. Regardless of this, the sound pressure of the ultrasonic wave received by the wave receiving element 3 decreases. As a result, there is a problem that the amount of change in the output of the wave receiving element 3 with respect to the amount of change in smoke density is relatively small, and the SN ratio is small.

  The present invention has been made in view of the above-described reasons, and improves the SN ratio in a configuration in which the presence or absence of a fire is determined based on the amount of ultrasonic attenuation in the monitoring space between the sound source unit and the receiving element. The purpose is to provide a fire detector.

In the invention of claim 1, a sound source unit capable of transmitting an ultrasonic wave, a control unit for controlling the sound source unit, a wave receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a wave receiving element A signal processing unit for determining the presence or absence of a fire based on the output of the signal, the signal processing unit is a monitoring space between the sound source unit and the receiving element based on the attenuation from the reference value of the output of the receiving element A smoke density estimating means for estimating the smoke density of the smoke, 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, The ultrasonic wave having a resonance frequency based on the propagation distance of the ultrasonic wave transmitted from the sound source unit and received by the wave receiving element is longer than the propagation time required for the ultrasonic wave to propagate from the sound source unit to the wave receiving element. over transmitting time controls the tone generator section so as to transmit continuously from the sound source unit, the sound source unit circumferential A plurality of types of ultrasonic waves having different numbers can be transmitted, and the signal processing unit is configured to output the output frequency of the sound source unit according to the type of suspended particles existing in the monitoring space and the smoke concentration, and the receiving element. Storage means storing relational data of attenuation from the reference value of output, relational data stored in the storage means and output of the receiving element for each ultrasonic wave transmitted from the sound source unit And a particle type estimation means for estimating the type of particles floating in the monitoring space using, and the smoke concentration estimation means, when the particles estimated by the particle type estimation means are smoke particles The smoke density in the monitoring space is estimated based on the attenuation amount from the reference value of the output of the receiving element with respect to the ultrasonic wave of a specific frequency .

  According to this configuration, the control unit propagates ultrasonic waves having a resonance frequency based on the propagation distance of the ultrasonic waves transmitted from the sound source unit and received by the wave receiving element, and at least the ultrasonic waves propagate from the sound source unit to the wave receiving element. Since the sound source unit is controlled so as to continuously transmit the sound from the sound source unit over a transmission time longer than the propagation time required to perform the resonance, resonance occurs between the sound source unit and the receiving element, Sound pressure increases. Therefore, the sound pressure of the ultrasonic wave received by the wave receiving element when there is no smoke particle in the monitoring space can be maintained high, and the amount of change in the output of the wave receiving element with respect to the amount of change in smoke concentration is relatively large, There is an advantage that the SN ratio is improved. In addition, in the ultrasonic wave reflected by the sound source unit or the receiving element due to resonance, the effective transmission distance is extended according to the number of reflections, and the amount of change in the output of the receiving element with respect to the amount of change in smoke density is more It gets bigger.

Further, according to this configuration, the signal processing unit, in the particle category estimation unit, and a relationship data stored in the output storage means of wave receiving devices of each ultrasound of each frequency that is transmitted from the sound source unit The type of particles floating in the monitoring space is estimated, and when the particles estimated by the particle type estimation means are smoke particles, the smoke density estimation means outputs the output of the receiving element to the ultrasonic wave of a specific frequency. The smoke concentration in the monitoring space is estimated based on the amount of attenuation from the reference value, so 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 Therefore, it is possible to reduce non-fire reports due to steam as compared with the scattered light type smoke detector and the reduced light type smoke detector, and it is also suitable for use in the kitchen or bathroom.

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

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

According to a third aspect of the present invention, in the first or second aspect of the invention, the sound source unit includes a single sound wave generating element capable of transmitting the plurality of types of ultrasonic waves, and the control unit includes a sound wave generating element. The sound source unit is controlled so that a plurality of types of ultrasonic waves are sequentially transmitted.

According to this configuration, it is possible to reduce the size and cost of the sound source unit as compared with a case where a plurality of sound wave generating elements capable of transmitting various types of ultrasonic waves are provided.
According to a fourth aspect of the present invention, in the first to third aspects of the present invention, there is a reflection surface that reflects the ultrasonic wave on a propagation path of the ultrasonic wave transmitted from the sound source unit and received by the receiving element. The reflecting surface is formed of a concave curved surface that is curved so as to collect the ultrasonic waves from the sound source section on the receiving element.
According to this configuration, since the ultrasonic wave from the sound source unit is collected by the wave receiving element on the reflection surface, it is possible to suppress a decrease in sound pressure due to the diffusion of the ultrasonic wave, and the wave receiving element with respect to the amount of change in smoke density The amount of change in output increases, and the SN ratio improves.
According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the control unit corrects a frequency of an ultrasonic wave transmitted from the sound source unit in accordance with a change in sound velocity due to a temperature change. It has a correction means.
According to this configuration, even if the resonance frequency between the sound source unit and the receiving element may fluctuate due to a change in sound speed due to a temperature change, the frequency of the ultrasonic wave transmitted from the sound source unit is the frequency. Since the correction means corrects the resonance frequency between the sound source unit and the receiving element after the fluctuation, the resonance is surely generated between the sound source unit and the receiving element, and the ultrasonic wave transmitted from the sound source unit is transmitted. The sound pressure will increase.

The invention according to claim 6 is a sound source unit capable of transmitting an ultrasonic wave, a control unit for controlling the sound source unit, a wave receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a wave receiving element A signal processing unit for determining the presence or absence of a fire based on the output of the signal, the signal processing unit is a monitoring space between the sound source unit and the receiving element based on the attenuation from the reference value of the output of the receiving element A smoke density estimating means for estimating the smoke density of the smoke, 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, The ultrasonic wave having a resonance frequency based on the propagation distance of the ultrasonic wave transmitted from the sound source unit and received by the wave receiving element is longer than the propagation time required for the ultrasonic wave to propagate from the sound source unit to the wave receiving element. It controls the tone generator section as over transmit time to transmit continuously from the sound source unit, the sound source unit, issued Characterized in that it is intended to generate ultrasonic waves by applying thermal shock to the air by the heating element temperature change caused by energization of the body portion.

According to this configuration, the control unit propagates ultrasonic waves having a resonance frequency based on the propagation distance of the ultrasonic waves transmitted from the sound source unit and received by the wave receiving element, and at least the ultrasonic waves propagate from the sound source unit to the wave receiving element. Since the sound source unit is controlled so as to continuously transmit the sound from the sound source unit over a transmission time longer than the propagation time required to perform the resonance, resonance occurs between the sound source unit and the receiving element, Sound pressure increases. Therefore, the sound pressure of the ultrasonic wave received by the wave receiving element when there is no smoke particle in the monitoring space can be maintained high, and the amount of change in the output of the wave receiving element with respect to the amount of change in smoke concentration is relatively large, There is an advantage that the SN ratio is improved. In addition, in the ultrasonic wave reflected by the sound source unit or the receiving element due to resonance, the effective transmission distance is extended according to the number of reflections, and the amount of change in the output of the receiving element with respect to the amount of change in smoke density is more It gets bigger. Furthermore, the sound source unit has a flat frequency characteristic, and the frequency of the generated ultrasonic wave can be changed over a wide range.

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

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

The invention of claim 8 is a sound source unit capable of transmitting ultrasonic waves, a control unit for controlling the sound source unit, a wave receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a wave receiving element A signal processing unit for determining the presence or absence of a fire based on the output of the signal, the signal processing unit is a monitoring space between the sound source unit and the receiving element based on the attenuation from the reference value of the output of the receiving element A smoke density estimating means for estimating the smoke density of the smoke, 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, The ultrasonic wave having a resonance frequency based on the propagation distance of the ultrasonic wave transmitted from the sound source unit and received by the wave receiving element is longer than the propagation time required for the ultrasonic wave to propagate from the sound source unit to the wave receiving element. It controls the tone generator section as over transmit time to transmit continuously from the sound source unit, sending from said tone generator A reflection surface that reflects ultrasonic waves is formed on the propagation path of the ultrasonic wave received by the wave receiving element, and the reflection surface collects ultrasonic waves from the sound source unit on the wave receiving element. It is characterized by comprising a concave curved surface curved into a sounding shape.

According to this configuration, the control unit propagates ultrasonic waves having a resonance frequency based on the propagation distance of the ultrasonic waves transmitted from the sound source unit and received by the wave receiving element, and at least the ultrasonic waves propagate from the sound source unit to the wave receiving element. Since the sound source unit is controlled so as to continuously transmit the sound from the sound source unit over a transmission time longer than the propagation time required to perform the resonance, resonance occurs between the sound source unit and the receiving element, Sound pressure increases. Therefore, the sound pressure of the ultrasonic wave received by the wave receiving element when there is no smoke particle in the monitoring space can be maintained high, and the amount of change in the output of the wave receiving element with respect to the amount of change in smoke concentration is relatively large, There is an advantage that the SN ratio is improved. In addition, in the ultrasonic wave reflected by the sound source unit or the receiving element due to resonance, the effective transmission distance is extended according to the number of reflections, and the amount of change in the output of the receiving element with respect to the amount of change in smoke density is more It gets bigger. Furthermore, since the ultrasonic waves from the sound source section are collected by the receiving element on the reflecting surface, it is possible to suppress a decrease in sound pressure due to the diffusion of ultrasonic waves, and the change in the output of the receiving element with respect to the amount of change in smoke density The amount increases and the signal to noise ratio improves.

The invention of claim 9 includes a sound source unit capable of transmitting ultrasonic waves, a control unit for controlling the sound source unit, a wave receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a wave receiving element A signal processing unit for determining the presence or absence of a fire based on the output of the signal, the signal processing unit is a monitoring space between the sound source unit and the receiving element based on the attenuation from the reference value of the output of the receiving element A smoke density estimating means for estimating the smoke density of the smoke, 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, The ultrasonic wave having a resonance frequency based on the propagation distance of the ultrasonic wave transmitted from the sound source unit and received by the wave receiving element is longer than the propagation time required for the ultrasonic wave to propagate from the sound source unit to the wave receiving element. It controls the tone generator section as over transmit time to transmit continuously from the sound source unit, wherein the control unit, the temperature In accordance with a change in sound speed due to the change and having a frequency correcting means for correcting the frequency of the ultrasonic waves transmitting from the sound source unit.

According to this configuration, the control unit propagates ultrasonic waves having a resonance frequency based on the propagation distance of the ultrasonic waves transmitted from the sound source unit and received by the wave receiving element, and at least the ultrasonic waves propagate from the sound source unit to the wave receiving element. Since the sound source unit is controlled so as to continuously transmit the sound from the sound source unit over a transmission time longer than the propagation time required to perform the resonance, resonance occurs between the sound source unit and the receiving element, Sound pressure increases. Therefore, the sound pressure of the ultrasonic wave received by the wave receiving element when there is no smoke particle in the monitoring space can be maintained high, and the amount of change in the output of the wave receiving element with respect to the amount of change in smoke concentration is relatively large, There is an advantage that the SN ratio is improved. In addition, in the ultrasonic wave reflected by the sound source unit or the receiving element due to resonance, the effective transmission distance is extended according to the number of reflections, and the amount of change in the output of the receiving element with respect to the amount of change in smoke density is more It gets bigger. Furthermore, even if the resonance frequency between the sound source unit and the receiving element may fluctuate due to a change in sound speed due to a temperature change , the frequency of the ultrasonic wave transmitted from the sound source unit varies depending on the frequency correction means. Since the resonance frequency between the sound source unit and the receiving element is corrected later, the resonance between the sound source unit and the receiving element is surely generated, and the sound pressure of the ultrasonic wave transmitted from the sound source unit increases. Will do.

  According to a tenth aspect of the present invention, in the ninth aspect, the frequency correction means is based on a time difference from when the sound source section transmits an ultrasonic wave until the ultrasonic wave is received by the receiving element. The frequency is corrected using the speed of sound obtained in this way.

According to this configuration, in the frequency correction unit, the frequency is corrected using the speed of sound obtained based on the time difference from when the sound source unit transmits the ultrasonic wave until the ultrasonic wave is received by the wave receiving element. Therefore, the configuration can be simplified as compared with the case where a means for obtaining the sound speed is separately provided.
The invention of claim 11 is the invention according to any one of claims 1 to 10, wherein the sound source section and the wave receiving element are arranged in parallel on the same plane, and are opposed to the sound source section and the wave receiving element. A reflection surface for reflecting the ultrasonic wave transmitted from the sound source unit toward the receiving element is formed at the position where the sound source is to be operated.
According to this configuration, the ultrasonic wave transmitted from the sound source unit does not directly reach the receiving element as a direct wave and is reflected by the reflecting surface at least once. Resonance is likely to occur between the two.

  The present invention can generate ultrasonic resonance between the sound source unit and the wave receiving element and increase the sound pressure of the ultrasonic wave. Therefore, the wave receiving element receives the wave in the absence of smoke particles in the monitoring space. The sound pressure of the ultrasonic wave that is waved can be kept high, the amount of change in the output of the wave receiving element with respect to the amount of change in smoke density is relatively large, the SN ratio is improved, and the effective transmission distance of the ultrasonic wave Is extended according to the number of reflections, so that the amount of change in the output of the wave receiving element with respect to the amount of change in smoke density is further increased.

(Embodiment 1)
As shown in FIG. 2, the fire detector according to the present embodiment includes a sound source unit 1 capable of transmitting ultrasonic waves, a control unit 2 that controls the sound source unit 1, and an ultrasonic wave transmitted from the sound source unit 1. A wave receiving element 3 that detects sound pressure and a signal processing unit 4 that determines the presence or absence of a fire based on the output of the wave receiving element 3 are provided. Here, as shown in FIG. 3, the sound source unit 1 and the wave receiving element 3 are arranged so as to face each other on the one surface side of the circuit board 5 made of a disk-shaped printed board. A control unit 2 and a signal processing unit 4 are provided. Around the wave receiving element 3, there is provided a sound insulating wall 6 made of a sound insulating plate for preventing ultrasonic waves generated outside the sound source unit 1 from entering the wave receiving element 3. In addition, a sound absorbing layer (not shown) for preventing the reflection of the ultrasonic wave transmitted from the sound source unit 1 is provided on the one surface of the circuit board 5, so that the super wave transmitted from the sound source unit 1 is provided. A sound wave can be prevented from being reflected by the circuit board 5 and incident on the wave receiving element 3, and interference of the reflected wave can be prevented. In particular, a continuous wave is transmitted as an ultrasonic wave transmitted from the sound source unit 1. It is effective when using.

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

  Here, as shown in FIG. 4, the sound source unit 1 includes a heat insulating layer (heat insulation) made of a porous silicon layer on one surface (upper surface in FIG. 4) side of a base substrate 11 made of a single crystal p-type silicon substrate. Layer) 12 is formed, and a heating element layer 13 made of a metal thin film is formed on the surface side of the heat insulating layer 12 as a heating element portion, and is electrically connected to the heating element layer 13 on the one surface side of the base substrate 11. A pair of pads 14 and 14 are formed. The planar shape of the base substrate 11 is a rectangular shape, and the planar shapes of the thermal insulating layer 12 and the heating element layer 13 are also rectangular. An insulating film (not shown) made of a silicon oxide film is formed on the surface of the base substrate 11 where the thermal insulating layer 12 is not formed on the one surface side.

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

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

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

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

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

  Further, as shown in FIG. 5, the capacitive microphone constituting the wave receiving element 3 is a rectangular frame 31 formed by providing a window hole 31a penetrating in the thickness direction in the silicon substrate. And a cantilever-type pressure receiving portion 32 disposed on one surface side of the frame 31 so as to straddle two opposing sides of the frame 31. Here, a thermal oxide film 35, a silicon oxide film 36 covering the thermal oxide film 35, and a silicon nitride film 37 covering the silicon oxide film 36 are formed on one surface side of the frame 31, and one end of the pressure receiving portion 32. Is supported by the frame 31 via the silicon nitride film 37, and the other end faces the silicon nitride film 37 in the thickness direction of the silicon substrate. Further, a fixed electrode 33a made of a metal thin film (for example, a chromium film) is formed on the surface of the silicon nitride film 37 facing the other end of the pressure receiving portion 32, and the silicon nitride film 37 at the other end of the pressure receiving portion 32 is formed. A movable electrode 33b made of a metal thin film (for example, a chromium film) is formed on the opposite side of the opposite surface. A silicon nitride film 38 is formed on the other surface of the frame 31. The pressure receiving portion 32 is constituted by a silicon nitride film formed in a separate process from the silicon nitride films 37 and 38 described above.

  In the wave receiving element 3 composed of a capacitance type microphone having the configuration shown in FIG. 5, a capacitor having the fixed electrode 33a and the movable electrode 33b as electrodes is formed, so that the pressure receiving portion 32 receives the pressure of the dense wave. As a result, the distance between the fixed electrode 33a and the movable electrode 33b changes, and the capacitance between the fixed electrode 33a and the movable electrode 33b changes. Therefore, if a DC bias voltage is applied between pads (not shown) provided on the fixed electrode 33a and the movable electrode 33b, a minute voltage change occurs between the pads according to the sound pressure of the ultrasonic waves. The sound pressure of ultrasonic waves can be converted into an electric signal.

  By the way, the signal processing unit 4 includes a smoke density estimation unit 41 that estimates the smoke density in the monitoring space between the sound source unit 1 and the wave receiving element 3 based on the attenuation amount from the reference value of the output of the wave receiving element 3. The smoke type estimation means 42 for comparing the smoke density estimated by the smoke density estimation means 41 with a predetermined threshold value to determine the presence or absence of a fire, and the sound source unit 1 transmits the ultrasonic wave, and then the ultrasonic wave A sound speed detecting means 43 for obtaining the sound speed based on the time difference until the wave receiving element 3 receives the wave, a temperature estimating means 44 for estimating the temperature of the monitoring space based on the sound speed obtained by the sound speed detecting means 43, Thermal type determination means 45 that compares the temperature estimated by the temperature estimation means 44 with a specified temperature to determine the presence or absence of a fire is 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 for analog-digital conversion of the output signal of the wave receiving element 3.

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

  The sound speed detection means 43 obtains the sound speed using the distance between the sound source unit 1 and the wave receiving element 3 and the time difference. Moreover, the temperature estimation means 44 estimates the temperature of the said monitoring space from a sound speed using the well-known relational expression of the sound speed in air and absolute temperature. The thermal determination means 45 determines “no fire” if the temperature estimated by the temperature estimation means 44 is lower than the specified temperature, while “fire” if the temperature is higher than the specified temperature. And the fire detection signal is output to the control unit 2. Here, even when the control unit 2 receives the fire detection signal from the thermal determination unit 45, the drive input waveform to the sound source unit 1 is generated so that an alarm sound including an audible sound wave is generated from the sound source unit 1. To control.

  By the way, in this embodiment, as shown in FIG. 1, each opposing surface of the sound source unit 1 and the wave receiving element 3 forms a first reflection surface Re1 and a second reflection surface Re2 that respectively reflect ultrasonic waves. Yes. Here, the surface of the sound source unit 1 facing the wave receiving element 3 forms the first reflecting surface Re1, and the surface of the wave receiving element 3 facing the sound source unit 1 forms the second reflecting surface Re2. With this configuration, the propagation path of the ultrasonic wave between the sound source unit 1 and the receiving element 3 is unique as in the air column having the first and second reflecting surfaces Re1 and Re2 on both end surfaces in the longitudinal direction. Resonance frequency. In other words, when the distance between the sound source unit 1 and the receiving element 3 is L, the frequency f () corresponding to the wavelength λ satisfying the relationship L = (n / 2) × λ (where n is a natural number). The wave propagation velocity is expressed as f = c / λ, where c is the resonance frequency in the ultrasonic wave propagation path between the sound source unit 1 and the wave receiving element 3. Therefore, when an ultrasonic continuous wave satisfying the relationship L = (n / 2) × λ is transmitted from the sound source unit 1, at least a part of the ultrasonic wave is reflected by the second reflecting surface Re2 and reflected. The reflected wave is reflected by the first reflecting surface Re2 to become a reflected wave, and the reflected wave is the same as the subsequent ultrasonic wave transmitted from the sound source unit 1. Resonating with overlapping phases, the sound pressure of the ultrasonic wave increases with time.

Therefore, in the present embodiment, the control unit 2 causes the sound source unit 1 to transmit an ultrasonic wave having a resonance frequency specific to the ultrasonic wave propagation path based on the distance L between the sound source unit 1 and the wave receiving element 3. By controlling the sound source unit 1, resonance is generated in the ultrasonic wave propagation path between the sound source unit 1 and the receiving element 3 to increase the sound pressure of the ultrasonic wave. In this case, in order to resonate in the ultrasonic wave propagation path between the sound source unit 1 and the wave receiving element 3, it is not a single-pulse ultrasonic wave but a plurality of cycles exceeding L / λ (hereinafter referred to as m cycle). Since it is necessary to transmit an ultrasonic wave from the sound source unit 1, the control unit 2 controls the sound source unit 1 so as to transmit a continuous wave of ultrasonic waves of m (> L / λ) period from the sound source unit 1. . In other words, the transmission time t _p (that is, t _p = m × λ / c) for continuously transmitting ultrasonic waves from the sound source unit 1 propagates between the sound source unit 1 and the receiving element 3. The sound source unit 1 is controlled by the control unit 2 so as to be longer than the time t _s (that is, t _s = L / c) required for performing (ie, t _p > t _s ). As a result, the ultrasonic wave transmitted from the sound source unit 1 resonates by overlapping with the reflected wave at least on the second reflecting surface Re2, so that the sound pressure of the ultrasonic wave between the sound source unit 1 and the wave receiving element 3 is reduced. The decrease can be suppressed. The wave receiving element 3 detects the sound pressure of the ultrasonic wave at the timing when the resonance occurs between the sound source unit 1 and the wave receiving element 3 and the sound pressure is saturated. Usually, since the sound pressure of the ultrasonic wave is saturated when the transmission of the ultrasonic wave from the sound source unit 1 is completed, as an example, the wave receiving element 3 simultaneously ends the transmission of the ultrasonic wave from the sound source unit 1. It is conceivable to detect the sound pressure of ultrasonic waves.

  Also, since the sound velocity c, which is the ultrasonic propagation velocity, changes according to the absolute temperature of the medium, the resonance frequency of the ultrasonic propagation path described above is not always constant, and is caused by the change in the sound velocity due to the temperature change of the medium. fluctuate. Therefore, in order to accurately match the frequency of the ultrasonic wave transmitted from the sound source unit 1 with the resonance frequency of the propagation path of the ultrasonic wave, the frequency of the ultrasonic wave transmitted from the sound source unit 1 is changed according to the change in sound velocity due to the temperature change. It is necessary to correct. Therefore, in the present embodiment, the control unit 2 includes frequency correction means (not shown) that corrects the frequency of the ultrasonic wave transmitted from the sound source unit 1 in accordance with the change in sound speed due to the temperature change. Therefore, even if the resonance frequency of the ultrasonic wave propagation path varies due to a change in sound velocity, the frequency of the ultrasonic wave transmitted from the sound source unit 1 is propagated by the frequency correction means after the fluctuation. Since the resonance frequency of the path is corrected, the resonance can be reliably generated by the ultrasonic wave transmitted from the sound source unit 1 between the sound source unit 1 and the wave receiving element 3. Further, the frequency correction means is obtained based on the time difference from when the sound source unit 1 transmits the ultrasonic wave to when the ultrasonic wave is received by the wave receiving element 3 in the above-described sound speed detection means 43. The frequency of the ultrasonic wave transmitted from the sound source unit 1 is corrected using the sound speed, and as a result, the configuration can be simplified as compared with the case where a means for obtaining the sound speed is separately provided.

  Specific examples of this embodiment will be given below. When the speed of sound c is 340 m / s and the distance L between the sound source unit 1 and the receiving element 3 is 34 mm, in order to satisfy the relationship of L = (n / 2) × λ, the supersonic wave transmitted from the sound source unit 1 The frequency f (= c / λ) of the sound wave may be set to 105 kHz (n = 21), for example. That is, 105 kHz is a resonance frequency of the propagation path, and by transmitting an ultrasonic wave having this frequency from the sound source unit 1, the sound pressure of the ultrasonic wave is increased by resonance. Here, as described above, since the sound source unit 1 needs to be controlled so that a continuous wave of ultrasonic waves having an m (> L / λ) period is transmitted from the sound source unit 1, the control unit 2 has, for example, an ultra-high frequency of 105 kHz. When transmitting a sound wave, the sound source unit 1 is controlled so as to continuously transmit an ultrasonic wave of at least about 11 cycles from the sound source unit 1. When transmitting ultrasonic waves of 105 kHz, if 105 cycles of ultrasonic waves are continuously transmitted from the sound source unit 1, the ultrasonic waves are reflected between the reflecting plates Re 1 and Re 2, or between the reflected waves, The sound pressure is greatly increased by the overlapping of the reflected wave and the direct wave from the sound source unit 1. In this configuration, the sound pressure of the ultrasonic wave detected by the wave receiving element 3 at the timing when the resonance occurs and the sound pressure is saturated is several tens of times that when a single pulse ultrasonic wave other than the resonance frequency is transmitted and received. Sound pressure.

  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 fire detector according to the present embodiment described above, the smoke density estimation means 41 determines the monitoring space between the sound source unit 1 and the wave receiving element 3 based on the attenuation amount from the reference value of the output of the wave receiving element 3. 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 surveillance space, so that responsiveness can be improved compared to scattered light smoke detectors, and non-fire reports can be reduced compared to dimmed smoke detectors.

  Further, in the present embodiment, resonance is generated in the ultrasonic wave propagation path between the sound source unit 1 and the wave receiving element 3, so that the resonance between the sound source unit 1 and the wave receiving element 3 is caused by resonance. Since the sound pressure of the sound wave is increased and the decrease in the sound pressure of the ultrasonic wave between the sound source unit 1 and the wave receiving element 3 can be suppressed, the wave receiving element 3 receives the sound in a state where there is no smoke particle in the monitoring space. The sound pressure of the ultrasonic wave that is waved can be maintained high, and the amount of change in the output of the wave receiving element 3 with respect to the amount of change in smoke density becomes relatively large. As a result, the SN ratio is improved. Furthermore, in the ultrasonic waves reflected by the reflection surfaces Re 1 and Re 2 due to resonance, the effective transmission distance is extended according to the number of reflections, and the ultrasonic waves are substantially transmitted between the sound source unit 1 and the wave receiving element 3. Reaches the receiving element 3 through a transmission distance several times the distance L. This also contributes to an increase in the amount of change in the output of the wave receiving element 3 with respect to the amount of change in the smoke density, as compared with the case where a non-resonant single-pulse ultrasonic wave is received by the wave receiving element 3. The attenuation of ultrasonic waves increases several times.

  Furthermore, in the fire detector according to the present embodiment, the sound speed detection means 43 determines the sound speed based on the time difference from when the sound source unit 1 transmits an ultrasonic wave until the ultrasonic wave is received by the wave receiving element 3. The temperature estimation means 44 estimates the temperature of the monitoring space based on the sound speed obtained by the sound speed detection means 43, and the thermal type judgment means 45 compares the temperature estimated by the temperature estimation means 44 with the specified temperature. Therefore, it is possible to detect the fire even when the temperature rises at the time of the fire without using a separate temperature detecting element, and to detect the fire more reliably.

(Embodiment 2)
The fire detector of the present embodiment has substantially the same basic configuration as that of the first embodiment, and is provided with a reflecting plate 7 shown in FIG. 6 so as to improve the reflectance of ultrasonic waves on the reflecting surfaces Re1 and Re2. This is different from the fire detector of the first embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 1, and description is abbreviate | omitted suitably.

  In the present embodiment, as shown in FIG. 6, a pair of reflecting plates 7 that are plate-like and are arranged to face each other are provided, and the sound source unit 1 and the wave receiving element 3 are respectively provided at substantially central portions of the reflecting plates 7. It is arranged. The surface of the sound source unit 1 facing the wave receiving element 3 and the surface of the wave receiving element 3 facing the sound source unit 1 are flush with the surface of each reflecting plate 7 (the surface facing the other reflecting plate 7). The surface of each reflector 7 forms reflection surfaces Re1 and Re2 together with the sound source unit 1 and the wave receiving element 3, respectively. According to this configuration, even if the ultrasonic wave spreads due to diffusion in the propagation path between the sound source unit 1 and the wave receiving element 3, the reflection surfaces Re 1 and 1 of the reflection plate 7 around the wave receiving element 3 or the sound source unit 1. Since it is returned to the propagation path by being reflected by Re2, it is possible to suppress a decrease in sound pressure due to the diffusion of ultrasonic waves, and the amount of change in the output of the receiving element with respect to the amount of change in smoke density increases. Thus, the SN ratio is improved.

  Further, in the present embodiment, the flat reflector 7 is exemplified, but the present invention is not limited to this configuration, and for example, a reflector 7 curved in a parabolic shape as shown in FIG. 7 may be used. If this reflecting plate 7 is used, each reflecting surface Re1, Re2 can be made into a concave-shaped curved surface, respectively, and when this receives the ultrasonic wave from the sound source part 1 by each reflecting surface Re1, Re2, it is a wave receiving element. 3 is collected, and a decrease in sound pressure due to diffusion of ultrasonic waves can be further suppressed. In the example of FIG. 7, both reflectors 7 are formed in a parabolic shape so as to suppress diffusion of both the ultrasonic wave reflected by the first reflecting surface Re1 and the ultrasonic wave reflected by the second reflecting surface Re2. However, it is possible to suppress the diffusion of ultrasonic waves only by making any one of the reflecting plates 7 parabolic.

  Furthermore, as shown in FIG. 8, the sound source unit 1 and the wave receiving element 3 are arranged side by side on one reflecting plate 7, and the first reflecting plate 7, the sound source unit 1, and the wave receiving element 3 perform the first reflection. The surface Re1 may be formed, and the other reflecting plate 7 may form the second reflecting surface Re2 alone. In this configuration, the ultrasonic wave transmitted from the sound source unit 1 does not directly reach the wave receiving element 3 as a direct wave, and is reflected at least once by the second reflecting surface Re2. Resonance is likely to occur with the wave receiving element 3. Here, if a parabolic plate is used as the reflection plate 7 on the side on which the second reflection surface Re2 is formed as shown in FIG. 9, the ultrasonic wave from the sound source unit 1 is received when the reflection surface Re2 is reflected. It is possible to further suppress the decrease in the sound pressure due to the sound wave collected by the wave element 3 and the diffusion of the ultrasonic waves. Similarly to the example of FIG. 7, both reflectors 7 may be parabolic. 8 and 9, the ultrasonic wave transmitted from the sound source unit 1 that forms the first reflection surface Re1 is reflected by the second reflection surface Re2 as described above, and the first reflection surface Re1 is reflected on the first reflection surface Re1. Since the wave is received by the wave receiving element 3 to be formed, the propagation path of the ultrasonic wave between the sound source unit 1 and the wave receiving element 3 is the first and second reflecting surfaces Re1, Re2 on both end faces in the longitudinal direction. Similar to an air column with a natural resonance frequency. That is, when the distance between the sound source unit 1 and the wave receiving element 3 is L, the distance between the first and second reflection surfaces Re1 and Re2 is L / 2, so L / 2 = The frequency f corresponding to the wavelength λ that satisfies the relationship (n / 2) × λ (where n is a natural number) is the resonance frequency in the ultrasonic wave propagation path between the sound source unit 1 and the wave receiving element 3.

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

(Embodiment 3)
The basic structure of the fire detector of the present embodiment is substantially the same as that of the first and second embodiments, 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, 2, and description is abbreviate | omitted suitably.

By the way, the inventors of the present application, as shown in FIG. 11, according to the type of suspended particles in the monitoring space between the sound source unit 1 and the wave receiving element 3, I got the knowledge that the relationship is different. Here, the sound pressure (hereinafter referred to as a reference sound pressure) received by the wave receiving element 3 in the absence of suspended particles in the monitoring space is defined as I ₀ , a dimming smoke densitometer (a dimming smoke detector). (I ₀ −I _x ), where I _x is the sound pressure received by the wave receiving element 3 in a state where suspended particles having a concentration of x% / m exist in the monitoring space. The value represented by / I ₀ is defined as the sound pressure attenuation rate, and in particular, the attenuation rate when x = 1 is defined as the unit attenuation rate. Here, it is assumed that the reference sound pressure I ₀ and the sound pressure I _x are detected under the same conditions except for the presence or absence of suspended particles in the monitoring space. “A” in FIG. 11 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 It is an approximate curve (black triangle is measurement data) showing the relationship with the unit attenuation rate of sound pressure, and the unit attenuation rate shown here is when the distance between the sound source unit 1 and the receiving element 3 is set to 30 cm. The data for each output frequency. Further, each data at the right end in FIG. 11 is data when the output frequency is 82 kHz, and FIG. 12 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. 12, the horizontal axis represents the output frequency, and the vertical axis represents the relative unit attenuation rate. The size of white smoke particles is about 800 nm, the size of black smoke particles is about 200 nm, and the size of steam particles is about several μm to 20 μm.

  Based on the above knowledge, in the present embodiment, the control unit 2 controls the sound source unit 1 so that plural types of ultrasonic waves having different frequencies are sequentially transmitted from the sound source unit 1, and the signal processing unit 4. Is at least the reference output of the wave receiving element 3 (the output of the wave receiving element 3 with respect to the reference sound pressure), the output frequency of the sound source unit 1 and the wave receiving element corresponding to the type of floating particles present in the monitoring space and the concentration of floating particles 3 relative data of the relative unit attenuation rate of the output (data extracted from FIG. 12 above), unit attenuation rate at a specific frequency (for example, 82 kHz) with respect to smoke particles (data extracted from FIG. 11 above) Is stored in the monitoring space using the storage means 48 storing the signal, the output of the wave receiving element 3 for each ultrasonic wave transmitted from the sound source unit 1 and the relational data stored in the storage means 48. Particle seeds The particle type estimation means 46 for estimating the frequency, and when the particles estimated by the particle type estimation means 46 are smoke particles, the attenuation from the reference value of the output of the wave receiving element 3 with respect to the ultrasonic wave of a specific frequency (for example, 82 kHz) Smoke density estimation means 47 for estimating the smoke density in the monitoring space based on the quantity, and smoke type judgment 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 Means 42.

  Below, the operation example of the fire detector of this embodiment is demonstrated with reference to the flowchart of FIG. First, a plurality of types of ultrasonic waves are sequentially transmitted from the sound source unit 1, and the output of the wave receiving element 3 for each ultrasonic wave is measured by the signal processing unit 4 (step S11). The particle type estimation means 46 obtains the sound pressure attenuation rate from the output of the wave receiving element 3 and the reference output stored in the storage means 48 for each output frequency (step S12), and the sound at the output frequency of 82 kHz. The ratio of the sound pressure attenuation rate at 20 kHz to the pressure attenuation rate is calculated (step S13). In the storage means 48, as the above relational data between the output frequency of the sound source unit 1 and the relative unit attenuation rate of the output of the wave receiving element 3, the relative unit at 20 kHz with respect to the relative unit attenuation rate at the output frequency of 82 kHz is stored. Attenuation rate ratio (in the case of FIG. 12, white smoke is 0, black smoke is 0.2, steam is 0.5) is stored, and the particle type estimation means 46 calculates the calculated attenuation rate ratio. Compared with the relational data stored in the storage means 48, the type of particle having the closest ratio of the attenuation rate in the relational data is estimated as the particle floating in the monitoring space (step S14). Here, if the estimated particles are smoke particles, the process proceeds to the processing in the smoke concentration estimating means 47 (step S15). Here, in the case of white smoke, as shown in FIG. 14, the relationship between the smoke density measured by the dimming smoke densitometer and the attenuation rate of the sound pressure is data that can be shown by a straight line, and other particles Therefore, the smoke concentration estimation means 47 is a unit stored in the storage means 48 of the attenuation factor of the output of the wave receiving element 3 with respect to the ultrasonic wave of a specific frequency (for example, 82 kHz) for the estimated particle type. A ratio with respect to the attenuation rate is calculated, and when the value of the ratio is y, it is estimated that the smoke density in the monitoring space corresponds to the smoke density y% / m in the evaluation with the dimming smoke densitometer (step S16). The smoke type determination means 42 compares the smoke density estimated in step S16 with a predetermined threshold value (for example, a smoke density that is 10% / m in the evaluation with the dimming smoke densitometer), and the estimated smoke. When the concentration is less than the above threshold, it is determined that “no fire”, while when it is equal to or greater than the above threshold, it is determined that “fire exists” and a fire detection signal is output to the control unit 2.

  In the above example, the particle type estimation means 46 uses the attenuation rate when the output frequency is 82 kHz and the attenuation rate when the output frequency is 20 kHz. However, the present invention is not limited to the combination of these output frequencies, and different combinations are possible. An output frequency may be used. Furthermore, attenuation rates for more output frequencies may be used, and in that case, the accuracy of estimation of the particle type can be improved. In this embodiment, the smoke density estimation means 47 targets one frequency as the specific frequency, but targets a plurality of frequencies as the specific frequency, and obtains an average value of the smoke density estimated for each specific frequency. In this case, the accuracy of smoke density estimation is improved. The signal processing unit 4 is constituted by a microcomputer, and the 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 for analog-digital conversion of the output signal of the wave receiving element 3.

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

  Further, in the present embodiment, the control unit 2 has a resonance frequency specific to the ultrasonic wave propagation path based on the distance L between the sound source unit 1 and the receiving element 3 as in the first and second embodiments. Propagation path of ultrasonic waves between the sound source unit 1 and the wave receiving element 3 by controlling the sound source unit 1 so as to transmit a continuous wave of ultrasonic waves of m (> L / λ) period from the sound source unit 1 Thus, resonance is generated to increase the sound pressure of the ultrasonic wave from the sound source unit 1. In short, the control unit 2 generates a plurality of types (for example, four types) of ultrasonic waves that are selected from resonance frequencies inherent in the ultrasonic wave propagation path between the sound source unit 1 and the receiving element 3 and have different frequencies from each other as the sound source. The sound source unit 1 is controlled to transmit from the unit 1.

In the present embodiment, the example in which the relationship data between the output frequency of the sound source unit 1 and the relative unit attenuation rate of the output of the receiving element 3 is stored in the storage unit 48 has been shown. Since the amount of attenuation (I ₀ −I _x ) from the reference value of the output of the wave receiving element 3 changes for each output frequency of the sound source unit 1 according to the type of particle, the above relationship stored in the storage means 48 The data may be data indicating the relationship between the output frequency of the sound source unit 1 and the attenuation amount from the reference value of the output of the wave receiving element 3. Instead of the above relative unit attenuation rate, for example, the wave receiving element Attenuation amount from the reference value of the output of 3 or the attenuation value obtained by dividing the attenuation amount from the reference value of the output of the receiving element 3 by the reference value (I ₀ ), or related data adopting the unit attenuation rate You may make it memorize | store in the memory | storage means 48. FIG.

  In the fire detector of the present embodiment described above, in the particle type estimation unit 46, the relationship between the output of the receiving element 3 for each ultrasonic wave transmitted from the sound source unit 1 and the storage unit 48 is stored. The type of particles floating in the monitoring space is estimated using the data, and when the particle estimated by the particle type estimation unit 46 is a smoke particle, the smoke density estimation unit 47 uses the ultrasonic wave of a specific frequency. The smoke density in the monitoring space is estimated based on the attenuation amount from the reference value of the output of the wave receiving element 3 with respect to the smoke density, and the smoke type estimating means 42 uses the smoke density estimated by the smoke density estimating means 47 and a predetermined threshold value. In order to judge the presence or absence of a fire, it is possible to eliminate the influence of background light, which is a problem with photoelectric fire detectors such as scattered light smoke detectors and dimming smoke detectors, Rabi required for scattered 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. Moreover, 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, the scattered light type smoke detector and the dimming type smoke detector can be used. In comparison, non-fire reports due to steam can be reduced, making it suitable for use in kitchens and bathrooms. 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 sound source unit 1 is constituted by a single sound wave generating element, and the control unit 2 sequentially changes the frequency of the drive input waveform applied to the sound source unit 1, so that a plurality of types having different frequencies from the sound source unit 1 can be obtained. However, the sound source unit 1 may be composed of a plurality of sound wave generating elements having different output frequencies. 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 to be transmitted from the sound source unit 1. It is possible to increase the sound pressure of the ultrasonic wave and 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.

  In addition, individual receiving elements 3 may be provided for various types of ultrasonic waves. In this case, piezoelectric elements having a relatively large Q value of resonance characteristics are used as the receiving elements 3. The sensitivity of the wave receiving element 3 can be improved by using each wave receiving element 3 for receiving ultrasonic waves of the respective resonance frequencies. Furthermore, by simultaneously driving multiple sound wave generating elements and transmitting multiple types of ultrasonic waves, it is possible to detect the amount of attenuation of the sound pressure of multiple types of ultrasonic waves at the same time. 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 changes (for example, changes in the concentration of suspended particles). When the sound source unit 1 and the wave receiving element 3 are arranged on the same reflection surface Re1 side as shown in FIGS. 8 and 9, the sound wave generating element constituting the sound source unit 1 is also used as the wave receiving element 3. In this case, the cost can be reduced by reducing the number of elements.

  The other configurations and functions are the same as those of the first and second embodiments. For example, also in the fire detector of this embodiment, the sound speed detecting means 43 is provided in the signal processing unit 4 as in the first embodiment shown in FIG. Further, a temperature estimation unit 44 and a thermal type determination unit 45 may be provided.

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

  Furthermore, the signal processing unit 4 periodically changes the output of the sound source unit 1 and the wave receiving element based on the output of the wave receiving element 3 with respect to an ultrasonic wave having a predetermined frequency (for example, 82 kHz which is the same as the specific frequency described above). If at least one of the control condition of the sound source section 1 by the control section 2 and the signal processing condition of the output of the receiving element 3 is changed so that the sensitivity fluctuation of 3 is canceled, the output fluctuation of the sound source section 1 Sensitivity fluctuations of the wave receiving element 3 can be periodically canceled, and long-term reliability is improved.

  Moreover, in each said embodiment, if the control part 2 is made to transmit the ultrasonic wave of the frequency which has an insect-proof effect from the sound source part 1, it can prevent that an insect penetrate | invades in the said monitoring space, Non-fire reports caused by insects can be reduced. Here, the control unit 2 may periodically transmit ultrasonic waves having a frequency having an insect-proofing effect separately from the ultrasonic waves having a frequency transmitted from the sound source unit 1 in order to estimate the smoke density. In order to estimate the smoke concentration, the frequency of the ultrasonic wave transmitted from the sound source unit 1 may be set to a frequency having an insect-proof effect.

It is a schematic side view which shows the principal part of Embodiment 1 of this invention. It is a block diagram which shows a structure same as the above. The principal part same as the above is shown, (a) is a schematic bottom view, (b) is a schematic side view. It is a schematic sectional drawing which shows the sound wave generation element used for the same as the above. The wave receiving element used for the above is shown, (a) is a partially broken schematic perspective view, and (b) is a schematic sectional view. It is a schematic side view which shows the principal part of Embodiment 2 of this invention. It is a schematic side view which shows the other example same as the above. It is a schematic side view which shows another example same as the above. It is a schematic side view which shows another example same as the above. It is a block diagram which shows the structure of Embodiment 3 of this invention. It is explanatory drawing which shows the relationship between the output frequency of a sound source part same as the above, and the unit attenuation rate of a sound pressure. It is explanatory drawing which shows the relationship between the output frequency of a sound source part same as the above, and a relative unit attenuation factor. 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.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sound source part 2 Control part 3 Receiver element 4 Signal processing part 7 Reflection board 11 Base substrate 12 Thermal insulation layer 13 Heating body layer (heating body part)
41 Smoke density estimating means 42 Smoke type judging means 46 Particle type estimating means 47 Smoke density estimating means 48 Storage means Re1 First reflecting surface Re2 Second reflecting surface

Claims (11)

A sound source unit capable of transmitting ultrasonic waves, a control unit for controlling the sound source unit, a receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a fire based on the output of the receiving element A signal processing unit for determining the presence or absence of smoke, and the signal processing unit is configured to estimate smoke concentration in a monitoring space between the sound source unit and the wave receiving element based on an attenuation amount from a reference value of the output of the wave receiving element. 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, and the control unit is transmitted from the sound source unit. Resonance frequency ultrasonic waves based on the propagation distance of the ultrasonic waves received by the receiving element are continuously transmitted over a transmission time longer than at least the propagation time required for the ultrasonic waves to propagate from the sound source to the receiving element. The sound source part is controlled to transmit from the sound source part automatically ,
The sound source unit can transmit a plurality of types of ultrasonic waves having different frequencies, and the signal processing unit is configured to output the output frequency of the sound source unit according to the type of suspended particles present in the monitoring space and the smoke concentration, and the Stored in the storage means for storing the relationship data with the attenuation amount from the reference value of the output of the receiving element, and the output of the receiving element for each ultrasonic wave transmitted from the sound source unit and stored in the storing means Particle type estimation means for estimating the type of particles floating in the monitoring space using the relationship data, and the smoke concentration estimation means is configured such that the particles estimated by the particle type estimation means are smoked. A fire detector for estimating a smoke concentration in the monitoring space based on an attenuation amount from a reference value of an output of the receiving element with respect to an ultrasonic wave of a specific frequency in the case of particles . The storage means stores, as the relationship data, relationship data between an output frequency of the sound source unit and an attenuation rate obtained by dividing an attenuation amount from a reference value of the output of the receiving element by a reference value. The fire detector according to claim 1. The sound source unit includes a single sound wave generating element capable of transmitting the plurality of types of ultrasonic waves, and the control unit controls the sound source unit so that the plurality of types of ultrasonic waves are sequentially transmitted from the sound wave generating elements. claim 1 or fire detector according to claim 2, characterized in that. A reflection surface that reflects ultrasonic waves is formed on a propagation path of ultrasonic waves that are transmitted from the sound source unit and received by the receiving element, and the reflection surface receives ultrasonic waves from the sound source unit. The fire detector according to any one of claims 1 to 3, wherein the fire detector is a concave curved surface that is curved so as to collect sound at the wave receiving element . The said control part has a frequency correction | amendment means which correct | amends the frequency of the ultrasonic wave transmitted from the said sound source part according to the change of the sound speed by a temperature change , The any one of Claim 1 thru | or 4 characterized by the above-mentioned. Fire detector as described in A sound source unit capable of transmitting ultrasonic waves, a control unit for controlling the sound source unit, a receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a fire based on the output of the receiving element A signal processing unit for determining the presence or absence of smoke, and the signal processing unit is configured to estimate smoke concentration in a monitoring space between the sound source unit and the wave receiving element based on an attenuation amount from a reference value of the output of the wave receiving element. 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, and the control unit is transmitted from the sound source unit. Resonance frequency ultrasonic waves based on the propagation distance of the ultrasonic waves received by the receiving element are continuously transmitted over a transmission time longer than at least the propagation time required for the ultrasonic waves to propagate from the sound source to the receiving element. The sound source part is controlled to transmit from the sound source part automatically,
The sound source unit, fire detectors you characterized in that to generate ultrasonic waves by applying thermal shock to the air by the temperature change of the heating element due to the energization of the heating element. The sound source unit is formed between the heat generating unit and the base substrate on the one surface side of the base substrate, and the heat generating unit and the base are formed on the one surface side of the base substrate. The fire detector according to claim 6 , further comprising a thermal insulating layer made of a porous layer that thermally insulates the substrate . A sound source unit capable of transmitting ultrasonic waves, a control unit for controlling the sound source unit, a receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a fire based on the output of the receiving element A signal processing unit for determining the presence or absence of smoke, and the signal processing unit is configured to estimate smoke concentration in a monitoring space between the sound source unit and the wave receiving element based on an attenuation amount from a reference value of the output of the wave receiving element. 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, and the control unit is transmitted from the sound source unit. Resonance frequency ultrasonic waves based on the propagation distance of the ultrasonic waves received by the receiving element are continuously transmitted over a transmission time longer than at least the propagation time required for the ultrasonic waves to propagate from the sound source to the receiving element. The sound source part is controlled to transmit from the sound source part automatically,
A reflection surface that reflects ultrasonic waves is formed on a propagation path of ultrasonic waves that are transmitted from the sound source unit and received by the receiving element, and the reflection surface receives ultrasonic waves from the sound source unit. fire detector you characterized by comprising a concave curved surface that is curved in shape to be collected in the wave receiving devices. A sound source unit capable of transmitting ultrasonic waves, a control unit for controlling the sound source unit, a receiving element for detecting the sound pressure of the ultrasonic wave transmitted from the sound source unit, and a fire based on the output of the receiving element A signal processing unit for determining the presence or absence of smoke, and the signal processing unit is configured to estimate smoke concentration in a monitoring space between the sound source unit and the wave receiving element based on an attenuation amount from a reference value of the output of the wave receiving element. 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, and the control unit is transmitted from the sound source unit. Resonance frequency ultrasonic waves based on the propagation distance of the ultrasonic waves received by the receiving element are continuously transmitted over a transmission time longer than at least the propagation time required for the ultrasonic waves to propagate from the sound source to the receiving element. The sound source part is controlled to transmit from the sound source part automatically,
The control unit may fire detector you further comprising a frequency correction means for correcting the frequency of the ultrasonic wave transmitting from the tone generator section in accordance with a change in sound velocity due to temperature changes.   The frequency correction means corrects the frequency using a sound speed obtained based on a time difference from when the sound source unit transmits an ultrasonic wave until the ultrasonic wave is received by the receiving element. The fire detector according to claim 9. The sound source unit and the wave receiving element are arranged in parallel on the same plane, and an ultrasonic wave transmitted from the sound source unit is placed on the wave receiving element at a position facing the sound source unit and the wave receiving element. The fire detector according to any one of claims 1 to 10, wherein a reflective surface that reflects toward the surface is formed.

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