JP4816526B2 - 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, and a wave receiving element 3 that detects the sound pressure of the 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, when smoke particles enter the monitoring space, the sound pressure of the ultrasonic waves from the sound source unit 1 decreases before reaching the wave receiving element 3, and the attenuation amount of the output of the wave receiving element 3 is substantially equal to the smoke concentration in the monitoring space. Since it increases in proportion, the presence or absence of a fire can be determined by estimating the smoke density based on this attenuation.

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

  By the way, in the ultrasonic fire detector described above, there is a problem that the change amount of the output of the wave receiving element 3 with respect to the change amount of the smoke density is relatively small and the SN ratio is small. Therefore, it is conceivable to increase the frequency of the ultrasonic wave transmitted from the sound source unit 1. If the frequency of the ultrasonic wave is increased, the amount of decrease in the sound pressure of the ultrasonic wave increases even if the smoke concentration in the monitoring space is constant, leading to an improvement in the SN ratio.

  However, the general wave receiving element 3 (microphone) does not support high-frequency (for example, 200 kHz) ultrasonic waves, and the sensitivity decreases as the ultrasonic frequency increases. Even if the frequency of the ultrasonic wave to be increased is increased, the sensitivity of the wave receiving element 3 is lowered, so that the SN ratio is not improved after all.

  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.

  According to the first aspect of the present invention, 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 sound pressure of a dense 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 estimation means for estimating the smoke density of the smoke, and a smoke type judgment means for judging the presence or absence of a fire by comparing the smoke density estimated by the smoke density estimation means with a predetermined threshold, , A first sound source that transmits a first ultrasonic wave having a first frequency higher than a fixed frequency at which the receiving element has sensitivity, and a second super frequency that has a second frequency higher than the first frequency by the fixed frequency. A second sound source that transmits sound waves, and the control unit transmits ultrasonic waves from both the first sound source and the second sound source to the monitoring space. By controlling the sound source unit so as to transmit simultaneously, the first ultrasonic wave and the second ultrasonic wave interfere with each other in the monitoring space to generate a beat wave which is a sparse wave of the fixed frequency, and the received wave The element is characterized by detecting a sound pressure of the beat wave.

  According to this configuration, the sound source unit transmits the first ultrasonic wave having the first frequency higher than the fixed frequency at which the receiving element has sensitivity, and is higher than the first frequency by the fixed frequency. A second sound source that transmits a second ultrasonic wave having a second frequency, and the control unit transmits the ultrasonic wave simultaneously from both the first sound source and the second sound source to the monitoring space. To control the first ultrasonic wave and the second ultrasonic wave to interfere with each other in the monitoring space to generate a beat wave that is a sparse wave of the fixed frequency, and the sound pressure of the beat wave is received at the receiving element. Since the frequency of the first and second ultrasonic waves transmitted from the sound source unit is set to be relatively high, the frequency of the beat wave received by the receiving element can be relatively low. it can. In other words, by increasing the frequency of the ultrasonic wave transmitted from the sound source unit, the attenuation rate of the ultrasonic wave due to suspended particles in the monitoring space is improved, and the frequency of the dense wave received by the receiving element is decreased. There is an advantage that the sensitivity of the wave element can be improved, and as a result, the SN ratio is improved.

  According to a second aspect of the present invention, in the first aspect of the invention, the first sound source and the second sound source can transmit a plurality of types of ultrasonic waves having different frequencies, and the signal processing unit is Storage means for storing relational data between 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 attenuation amount from the reference value of the output of the receiving element, from the sound source unit Particle type estimation means for estimating the type of particles floating in the monitoring space using the output of the receiving element for each ultrasonic wave transmitted at each frequency and the relational data stored in the storage means; And the smoke concentration estimation means is based on an attenuation amount from a reference value of the output of the receiving element with respect to an ultrasonic wave of a specific frequency when the particle estimated by the particle type estimation means is a smoke particle. Estimating smoke density in the surveillance space And features.

  According to this configuration, in the signal processing unit, the particle type estimation unit uses the output of the receiving element for each ultrasonic wave of each frequency transmitted from the sound source unit and the relational data stored in the storage unit. Estimate the type of particles floating in the monitoring space, and when the particles estimated by the particle type estimation means are smoke particles, the smoke concentration estimation means uses the output standard of the receiving element for ultrasonic waves of a specific frequency. Since the smoke concentration in the monitoring space is estimated based on the amount of attenuation from the value, 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 identifying means. Therefore, it is possible to reduce non-fire reports caused by steam as compared with the scattered light smoke detector and the reduced light smoke detector, and it is also suitable for use in the kitchen or bathroom.

  According to a third aspect of the present invention, in the second aspect of the present invention, the storage 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.

  The invention of claim 4 is the invention of claim 2 or claim 3, wherein the first sound source and the second sound source 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 sound source unit so that a plurality of types of ultrasonic waves are sequentially transmitted from each of the sound wave generating elements.

  According to this configuration, it is possible to reduce the size and cost of the sound source unit as compared with the case where each of the first sound source and the second sound source includes a plurality of sound wave generating elements capable of transmitting various ultrasonic waves. Become.

  According to a fifth aspect of the present invention, the sound source unit according to any one of the first to fourth aspects of the present invention is characterized by applying a thermal shock to the air due to a change in temperature of the heat generating unit accompanying energization of the heat generating unit. It is characterized by generating sound waves.

  According to this configuration, 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 sixth aspect of the present invention, in the fifth aspect of the present invention, the sound source section includes the heating element section formed on the one surface side of the base substrate, and the heating element section 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.

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

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

  According to an eighth aspect of the present invention, in any one of the first to sixth aspects of the present invention, a cylindrical shape in which one end surface in the longitudinal direction is opened as a radiation side end surface between the first sound source and the receiving element. A first cylinder that narrows the diffusion range of the ultrasonic wave by passing the ultrasonic wave from the first sound source through the internal space, and between the second sound source and the receiving element, A second cylindrical body is provided which is formed in a cylindrical shape having one end face in the longitudinal direction opened as a radiation side end face, and narrows the diffusion range of the ultrasonic wave by passing the ultrasonic wave from the second sound source through the internal space. The first and second cylinders are arranged so that the ultrasonic waves radiated from the respective radiation side end faces interfere with each other in front of the receiving element.

  According to this configuration, the first cylindrical body is formed in a cylindrical shape whose one end surface in the longitudinal direction is opened as a radiation side end surface, and narrows the diffusion range of the ultrasonic wave by passing the ultrasonic wave from the first sound source through the internal space. Is provided between the first sound source and the wave receiving element, and is formed in a cylindrical shape with one end surface in the longitudinal direction opened as a radiation side end surface. By passing the ultrasonic wave from the second sound source through the internal space, Since the second cylinder that narrows the diffusion range is provided between the second sound source and the receiving element, each ultrasonic wave from the first sound source and the second sound source passes through the first and second cylinders. The diffusion is suppressed by passing, and the decrease in the sound pressure due to the diffusion of the ultrasonic wave between the sound source unit and the receiving element can be suppressed. In addition, since the beat wave is generated outside the first and second cylinders, even when the frequency of the beat wave received by the receiving element is low, the viscous resistance of the inner peripheral surface of each cylinder is caused. The beat wave will not be attenuated. Therefore, the amount of change in the output of the wave receiving element with respect to the change in smoke density is increased, and the SN ratio is improved.

  According to a ninth aspect of the present invention, in one of the first to sixth aspects of the present invention, one end surface in the longitudinal direction radiates between one of the first sound source and the second sound source and the receiving element. A cylindrical body that is formed in a cylindrical shape that is opened as a side end surface and that narrows the diffusion range of the ultrasonic wave by passing ultrasonic waves from the one side through the internal space is provided. The acoustic wave is arranged so as to interfere with an ultrasonic wave transmitted from the other of the first sound source and the second sound source and before the receiving element.

  According to this configuration, between one of the first sound source and the second sound source and the receiving element, one end surface in the longitudinal direction is formed in a cylindrical shape opened as a radiation side end surface, and ultrasonic waves from one side are transmitted into the internal space. Since the cylindrical body that narrows the diffusion range of the ultrasonic wave is provided by passing through the ultrasonic wave, diffusion of the ultrasonic wave from the one side is suppressed by passing through the cylindrical body, and the ultrasonic wave between the sound source unit and the receiving element is suppressed. A decrease in sound pressure due to the diffusion of sound waves can be suppressed. Further, since the frequency of the ultrasonic wave transmitted from the other of the first sound source and the second sound source can be set without being restricted by the provision of the cylindrical body, the first frequency and the second frequency A fixed frequency corresponding to the difference can be freely set. That is, the frequency of the beat wave can be matched with the frequency having high wave receiving sensitivity at the wave receiving element.

  The present invention improves the attenuation rate of ultrasonic waves due to suspended particles in the monitoring space by increasing the frequency of each of the first and second ultrasonic waves transmitted from the sound source unit, and beats received by the wave receiving element. The sensitivity of the wave receiving element can be improved by lowering the wave frequency, and as a result, the SN ratio is improved.

(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 a sparse wave ( A wave receiving element 3 that detects sound pressure of a beat wave (to be described later) 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. In the vicinity of the wave receiving element 3, there is provided a sound insulating wall 6 made of a sound insulating plate that prevents the dense wave 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 in accordance with the sound pressure of the dense wave. The sound pressure of the dense wave 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 The sound speed detecting means 43 for obtaining the sound speed based on the time difference until the dense wave corresponding to is received by the wave receiving element 3, and the temperature for estimating the temperature of the monitoring space 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 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 from the reference value of the output of the wave receiving element 3 that detects the sound pressure of the dense wave from the sound source section 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 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 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. Note that the sound velocity detection means 43 periodically transmits a sparse wave having a predetermined frequency separately from the ultrasonic wave transmitted from the sound source unit 1 in order to estimate the smoke density, and the sparse wave is received by the wave receiving element 3. The sound speed may be obtained based on the time difference until the wave is generated, or the sound speed may be obtained using an ultrasonic wave transmitted from the sound source unit 1 in order to estimate the smoke density.

  By the way, if the frequency of the ultrasonic wave transmitted from the sound source unit 1 is increased, the amount of decrease in the sound pressure of the ultrasonic wave increases even if the smoke concentration in the monitoring space is constant, leading to an improvement in the SN ratio. Then, the frequency of the ultrasonic wave transmitted from the sound source unit 1 is set to be relatively high. However, the general receiving element 3 does not support high frequency (for example, 200 kHz) ultrasonic waves, and there is a problem that the sensitivity decreases as the ultrasonic frequency increases. This problem is solved by adopting the configuration.

  That is, the sound source unit 1 of the present embodiment includes a first sound source SP1 that transmits ultrasonic waves of a first frequency (hereinafter also referred to as first ultrasonic waves), as shown in FIG. As shown in b), it has a second sound source SP2 that transmits an ultrasonic wave having a second frequency higher than the first frequency (hereinafter also referred to as a second ultrasonic wave). Both the first sound source SP1 and the second sound source SP2 are arranged in parallel on the same surface so as to face the wave receiving element 3. Here, the second frequency is set higher than the first frequency by a predetermined fixed frequency, and the fixed frequency is set at least lower than the first frequency. Further, the control unit 2 controls the first sound source SP1 and the second sound source SP2 so as to simultaneously transmit ultrasonic waves from both the first sound source SP1 and the second sound source SP2 to the monitoring space. Accordingly, the ultrasonic waves transmitted from each of the first sound source SP1 and the second sound source SP2 interfere with each other due to the nonlinearity of the medium (air) in the monitoring space, and both ultrasonic waves as shown in FIG. A beat wave, which is a sparse / dense wave, having a frequency (fixed frequency) corresponding to the difference between the two frequencies is generated. In FIG. 1, “A” and “B” represent a first ultrasonic wave and a second ultrasonic wave, respectively, and “C” represents a beat wave. That is, in the monitoring space, when the first ultrasonic wave (“A” in FIG. 1A) and the second ultrasonic wave (“B” in FIG. 1B) are incident as primary waves. A beat wave having a fixed frequency, which is the difference between the second frequency and the first frequency (“C” in FIG. 1C), is generated as a secondary wave.

  On the other hand, as the wave receiving element 3, an element having sufficient sensitivity with respect to the above-mentioned fixed frequency dense wave is adopted, and the wave receiving element 3 transmits from each of the first sound source SP1 and the second sound source SP2. Instead of detecting the sound pressure of the ultrasonic wave itself, the sound pressure of the beat wave is detected. Therefore, according to the configuration of the present embodiment, the frequency of each of the first and second ultrasonic waves transmitted from the sound source unit 1 (that is, the first frequency and the second frequency) is set to be relatively high, while receiving the wave. The frequency (that is, the fixed frequency) of the beat wave received by the element can be set low.

  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, the frequency of the first ultrasonic wave transmitted from the first sound source SP1 is set to 200 kHz, and the second sound source The frequency of the second ultrasonic wave transmitted from SP2 is set to 220 kHz. Here, the control unit 2 controls the sound source unit 1 so as to continuously transmit ultrasonic waves of, for example, about 100 cycles from the first sound source SP1 and the second sound source SP2. In this case, a beat wave having a fixed frequency (= 20 kHz) that is a difference between the first frequency (= 200 kHz) and the second frequency (= 220 kHz) is generated in the monitoring space. Therefore, the wave receiving element 3 detects the sound pressure of a 20 kHz dense wave, and the general wave receiving element 3 (not limited to the above-described capacitance type microphone, for example, includes an electret condenser microphone). However, sound pressure can be detected with sufficient sensitivity. Here, since the ultrasonic waves transmitted from the sound source unit 1 are 200 kHz and 220 kHz, if there is smoke particles in the monitoring space, a sound pressure drop equivalent to an ultrasonic wave having a frequency corresponding to 200 kHz occurs, and the wave receiving element 3 The amount of output attenuation is relatively large.

  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.

  Further, in the present embodiment, the first sound source SP1 and the second sound source SP2 are arranged on the same plane to constitute the sound source unit 1, and the receiving element 3 is arranged so as to face the sound source unit 1 through the monitoring space. However, the first sound source SP1 and the second sound source SP2 are arranged so as to face each other through the monitoring space, and are received at the central portion in the facing direction of the first sound source SP1 and the second sound source SP2 in the monitoring space. The wave element 3 may be arranged.

  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.

  In the present embodiment, the sound source unit 1 includes a first sound source SP1 that transmits ultrasonic waves of the first frequency and a second sound source SP2 that transmits ultrasonic waves of the second frequency. A beat wave is generated by controlling the sound source unit 1 so that ultrasonic waves are simultaneously transmitted from both the first sound source SP1 and the second sound source SP2 to the monitoring space, and the receiving element 3 generates sound pressure of the beat wave. Since the frequency of each ultrasonic wave transmitted from the sound source unit 1 (that is, the first frequency and the second frequency) is set relatively high, the beat wave received by the wave receiving element 3 is detected. Can be set relatively low (that is, a fixed frequency). Therefore, by increasing the frequency of each ultrasonic wave transmitted from the sound source unit 1 to increase the amount of decrease in the sound pressure of the ultrasonic wave due to the smoke particles in the monitoring space, the density received by the wave receiving element 3 is increased. By reducing the frequency of the wave, the general receiving element 3 can detect the sound pressure with sufficient sensitivity, resulting in an advantage that the SN ratio is improved.

  Furthermore, in the fire detector according to the present embodiment, the sound speed detection means 43 obtains the sound speed based on the time difference from when the sound source unit 1 transmits an ultrasonic wave until the dense 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 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 a basic configuration substantially the same as that of the first embodiment, and a cylindrical body 7 formed between the sound source unit 1 and the wave receiving element 3 is arranged as shown in FIG. The provided point 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.

  The cylindrical body 7 is a straight tubular rectangular tube whose both end faces in the longitudinal direction are closed. As shown in FIG. 6, the sound source unit 1 (that is, the first sound source) is disposed on one end face in the longitudinal direction (left end face in FIG. 6). The SP1 and the second sound source SP2) are disposed, and the wave receiving element 3 is disposed on the other end surface (the right end surface in FIG. 6), and the ultrasonic waves from the sound source unit 1 are propagated through the internal space. By providing this cylindrical body 7, diffusion of the ultrasonic wave transmitted from the sound source unit 1 is suppressed by passing through the internal space of the cylindrical body 7, and therefore, between the sound source unit 1 and the wave receiving element 3. A decrease in sound pressure due to the diffusion of ultrasonic waves can be suppressed. In this configuration, since the inside of the cylinder 7 serves as a monitoring space, for example, a hole (not shown) for guiding smoke or the like is formed in the side surface along the longitudinal direction of the cylinder 7.

Further, in the present embodiment, the cylindrical body 7 has a specific resonance frequency in the same manner as a known acoustic tube whose both end faces in the longitudinal direction are closed. In other words, when the longitudinal dimension of the cylindrical body 7 is L, the frequency f (wave propagation velocity) corresponding to the wavelength λ satisfying the relationship of L = (n / 2) × λ (where n is a natural number). (represented by f = c / λ as c) is the resonance frequency of the cylinder 7. Therefore, when a continuous wave of ultrasonic waves satisfying the relationship of L = (n / 2) × λ is incident into the cylindrical body 7 from the end face in the longitudinal direction, at least a part of the ultrasonic wave is at both ends in the longitudinal direction of the cylindrical body 7 By repeating the reflection on the surface, the reflected wave and the direct wave from the sound source unit 1 overlap and resonate, and the sound pressure of the ultrasonic wave increases inside the cylindrical body 7. Therefore, in the present embodiment, the control unit 2 controls the sound source unit 1 so as to transmit the ultrasonic wave having the resonance frequency inherent to the cylinder 7 from the first sound source SP1 and the second sound source SP2. 7 is caused to resonate and the sound pressure of the ultrasonic wave from the sound source unit 1 is increased. In this case, in order to cause resonance in the cylindrical body 7, it is necessary to transmit ultrasonic waves having a plurality of cycles (hereinafter referred to as m cycles) exceeding L / λ from the sound source unit 1. The sound source unit 1 is controlled so that a continuous wave of ultrasonic waves having an m (> L / λ) period is transmitted 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 both ends in the longitudinal direction of the cylindrical body 7. The sound source unit 1 is controlled by the control unit 2 so as to be longer than the propagation time t _s (that is, t _s = L / c) required (ie, t _p > t _s ). The wave receiving element 3 detects the sound pressure of the beat wave at a timing when resonance occurs in the cylindrical body 7 and the sound pressure of the ultrasonic wave 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 the beat wave.

  Specific examples of this embodiment will be given below. When the speed of sound c is 340 m / s and the longitudinal dimension L of the cylindrical body 7 is 34 mm, the first ultrasonic wave transmitted from the first sound source SP1 is satisfied in order to satisfy the relationship of L = (n / 2) × λ. Is set to 200 kHz (n = 40), and the frequency of the second ultrasonic wave transmitted from the second sound source SP2 is set to 220 kHz (n = 44). Here, as described above, since the sound source unit 1 needs to be controlled so that a continuous wave of ultrasonic waves of m (> L / λ) period is transmitted from the sound source unit 1, the control unit 2 has, for example, about 100 cycles. The sound source unit 1 is controlled such that each ultrasonic wave is continuously transmitted from the first sound source SP1 and the second sound source SP2. In this case, a beat wave having a fixed frequency (= 20 kHz) that is a difference between the first frequency (= 200 kHz) and the second frequency (= 220 kHz) is generated in the monitoring space. Therefore, the sound receiving element 3 detects the sound pressure of a 20 kHz dense wave, and the general wave receiving element 3 can detect the sound pressure with sufficient sensitivity. Here, since the ultrasonic waves transmitted from the sound source unit 1 are 200 kHz and 220 kHz, if there is smoke particles in the monitoring space, a sound pressure drop equivalent to an ultrasonic wave having a frequency corresponding to 200 kHz occurs, and the wave receiving element 3 The amount of output attenuation is relatively large.

  In the present embodiment, the first sound source SP1 and the second sound source SP2 are arranged side by side on one end surface in the longitudinal direction of the cylindrical body 7, and the wave receiving element 3 is disposed on the other end surface in the longitudinal direction of the cylindrical body 7. However, as shown in FIG. 7, the first sound source SP1 and the second sound source SP2 are arranged on each end face in the longitudinal direction of the cylindrical body 7, and are received by the central portion on the side surface along the longitudinal direction of the cylindrical body 7. The wave element 3 may be arranged.

  In the fire detector of the present embodiment described above, the ultrasonic wave transmitted from the sound source unit 1 is provided by providing the cylindrical body 7 in the ultrasonic wave propagation path between the sound source unit 1 and the wave receiving element 3. Since diffusion is suppressed by passing through the internal space of the cylinder 7 and a decrease in sound pressure due to diffusion of ultrasonic waves between the sound source unit 1 and the wave receiving element 3 can be suppressed, smoke is not contained in the monitoring space. The sound pressure of the beat wave received by the wave receiving element 3 in the absence of particles 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. Has the effect of improving.

  Further, in the present embodiment, resonance is caused in the cylindrical body 7 and the sound pressure of the ultrasonic wave from the sound source unit 1 is increased, so that the sound pressure between the sound source unit 1 and the wave receiving element 3 is reduced. This can be further suppressed, and the amount of change in the output of the wave receiving element 3 with respect to the amount of change in smoke concentration increases, and the SN ratio is further improved. Moreover, in the ultrasonic wave that repeats reflection on the end face in the longitudinal direction of the cylindrical body 7 due to resonance, the effective transmission distance is extended according to the number of reflections, and the ultrasonic wave is substantially the dimension in the longitudinal direction of the cylindrical body 7. It reaches the wave receiving element 3 through a transmission distance several times 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.

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

(Embodiment 3)
The fire detector of this embodiment has a basic configuration that is substantially the same as that of the second embodiment, and the configuration of the cylinder is different from that of the fire detector of the second embodiment. In addition, the same code | symbol is attached | subjected to the component similar to Embodiment 2, and description is abbreviate | omitted suitably.

  In the present embodiment, as a cylindrical body, as shown in FIG. 8, the first cylindrical body 71 whose one end surface in the longitudinal direction is opened as a radiation side end surface 71a and the other end surface in the longitudinal direction is covered with the first sound source SP1, and One end surface in the direction is opened as a radiation side end surface (not shown) and the other end surface in the longitudinal direction is covered with the second sound source SP2, and the second cylinder 72 is used. Both the cylinders 71 and 72 have their radiation side end faces 71a (opening faces) directed to the wave receiving element 3, and ultrasonic waves radiated from both the radiation side end faces 71a are in front of the wave receiving element 3 (the wave receiving element 3 and the radiation). It is arranged in a V shape so as to interfere with each other (between the side end surfaces 71a). Thereby, the ultrasonic waves respectively transmitted from the first sound source SP1 and the second sound source SP2 are radiated from the radiation side end face 71a through the respective cylinders 71 and 72, and intersect each other before the wave receiving element 3 so that the medium The non-linearity of (air) interferes with each other to generate beat waves.

Further, in the present embodiment, since one end surface in the longitudinal direction of each cylindrical body 71, 72 is open, each cylindrical body 71, 72 is similar to a known acoustic tube in which one end surface in the longitudinal direction is closed, Has a unique resonance frequency. In other words, when the longitudinal dimension of the cylinders 71 and 72 is L, the wavelength satisfying the relationship of L = (1/4 + n / 2) × λ (where n = 0, 1, 2, 3,...). A frequency f (= c / λ) corresponding to λ is the resonance frequency of the cylinders 71 and 72. Therefore, when a continuous wave of ultrasonic waves satisfying the relationship of L = (1/4 + n / 2) × λ enters the cylindrical bodies 71 and 72 from the end faces in the longitudinal direction, at least a part of the ultrasonic waves is converted into the cylindrical bodies 71, 72. By repeating the reflection at both end faces in the longitudinal direction of 72, the reflected wave and the direct wave from the sound source unit 1 overlap and resonate, and the sound pressure of the ultrasonic wave increases inside the cylinders 71 and 72. Therefore, if the control unit 2 controls the sound source unit 1 so that the ultrasonic waves having the resonance frequency inherent to the cylinders 71 and 72 are transmitted from the first sound source SP1 and the second sound source SP2, the cylinders 71, It is possible to increase the sound pressure of the ultrasonic wave from the sound source unit 1 by causing resonance in 72. In this case, in order to cause resonance in the cylinders 71 and 72, the control unit 2 causes the sound source unit 1 to transmit a continuous wave of ultrasonic waves having an m (> L / λ) period from the sound source unit 1. Control. In other words, the transmission time t _p (= m × λ / c) in which the ultrasonic waves are continuously transmitted from the sound source unit 1 is propagated between the longitudinal ends of the cylindrical bodies 71 and 72. The sound source unit 1 is controlled by the control unit 2 so as to be longer than the required propagation time t _s (= L / c) (that is, t _p > t _s ). When one end face is an open end, as is well known, a node of ultrasonic sound pressure (that is, an antinode of air moving speed) is generated slightly outside the open end by ΔL, so that the resonance frequency is obtained. If the length L used at this time is corrected by the above ΔL (correction of the opening end), a more accurate resonance frequency can be obtained.

  Specific examples of this embodiment will be given below. When the speed of sound c is 340 m / s and the longitudinal dimension L of each of the cylinders 71 and 72 is 34 mm, the first sound source SP1 is transmitted to satisfy the relationship L = (1/4 + n / 2) × λ. The frequency of the first ultrasonic wave may be set to 202.5 kHz (n = 40), and the frequency of the second ultrasonic wave transmitted from the second sound source SP2 may be set to 222.5 kHz (n = 44). Here, as described above, since the sound source unit 1 needs to be controlled so that a continuous wave of ultrasonic waves of m (> L / λ) period is transmitted from the sound source unit 1, the control unit 2 has, for example, about 100 cycles. The sound source unit 1 is controlled such that each ultrasonic wave is continuously transmitted from the first sound source SP1 and the second sound source SP2. In this case, a beat wave having a fixed frequency (= 20 kHz) that is a difference between the first frequency (= 202.5 kHz) and the second frequency (= 222.5 kHz) is generated in the monitoring space. Therefore, the sound receiving element 3 detects the sound pressure of a 20 kHz dense wave, and the general wave receiving element 3 can detect the sound pressure with sufficient sensitivity. Here, since the ultrasonic waves transmitted from the sound source unit 1 are 202.5 kHz and 222.5 kHz, if there is smoke particles in the monitoring space, a sound pressure drop equivalent to that of an ultrasonic wave having a frequency equivalent to 200 kHz occurs. The amount of attenuation of the output of the wave element 3 is relatively large.

  According to the configuration of the present embodiment described above, a beat wave is generated outside the first and second cylinders 71 and 72. Therefore, when the frequency of the beat wave received by the wave receiving element 3 is low. However, the beat wave is not attenuated due to the viscous resistance of the inner peripheral surfaces of the cylinders 71 and 72. That is, when the cross-sectional areas (tube diameters) of the cylinders 71 and 72 are small, the density wave is less than a certain frequency due to the viscous resistance of the inner peripheral surfaces of the cylinders 71 and 72 when the dense waves pass through the cylinders 71 and 72. However, in the configuration of the present embodiment, a high frequency (that is, the first frequency and the second frequency) does not decrease in the dense waves passing through the cylinders 71 and 72. Frequency). Therefore, the amount of change in the output of the wave receiving element 3 with respect to the change in smoke density is increased, and the SN ratio is improved.

  Moreover, although the example which provides the cylindrical bodies 71 and 72 in each of 1st sound source SP1 and 2nd sound source SP2 was shown in this embodiment, as shown in FIG. 9, the 1st which lets the ultrasonic wave from 1st sound source SP1 pass is shown. Only the cylindrical body 71 is provided, and the ultrasonic wave radiated from the radiation side end surface 71a of the cylindrical body 71 and the ultrasonic wave transmitted from the second sound source SP2 are caused to interfere with each other in front of the wave receiving element 3. It may be. In the example of FIG. 9, the first sound source SP <b> 1 and the second sound source SP <b> 2 radiate ultrasonic waves from the side toward the radiation side end face 71 a of the first cylindrical body 71 and the wave receiving element 3. The second sound source SP2, the cylindrical body 71, and the wave receiving element 3 are arranged. In this configuration, since the frequency of the ultrasonic wave transmitted from the second sound source SP2 can be set without being restricted by the provision of the cylindrical body 71, the difference between the first frequency and the second frequency is set. A fixed frequency corresponding to can be freely set. That is, the frequency of the beat wave can be matched with the frequency at which the wave receiving sensitivity at the wave receiving element 3 is highest.

  A specific example of the configuration of FIG. 9 is given below. In order to satisfy the relationship of L = (1/4 + n / 2) × λ when the sound velocity c is 340 m / s and the longitudinal dimension L of the cylindrical body 71 is 34 mm, the first sound transmitted from the first sound source SP1 is transmitted. What is necessary is just to set the frequency of an ultrasonic wave to 202.5 kHz (n = 40). On the other hand, the frequency of the second ultrasonic wave transmitted from the second sound source SP2 does not have to be matched with the resonance frequency of the cylindrical body 71, so it is desirable to set based on the frequency characteristics of sensitivity in the wave receiving element 3. . That is, when the sensitivity of the wave receiving element 3 is maximized with respect to a 12 kHz dense wave, for example, it is desirable to set the second frequency to 214.5 kHz, which is 12 kHz higher than the first frequency (= 202.5 kHz). In this case, a beat wave having a fixed frequency (= 12 kHz) that is a difference between the first frequency (= 202.5 kHz) and the second frequency (= 214.5 kHz) is generated in the monitoring space. Therefore, the wave receiving element 3 detects the sound pressure of a 12 kHz dense wave, and can be operated at a frequency at which the sensitivity is maximized.

  Note that the relationship between the first sound source SP1 and the second sound source SP2 in the configuration of FIG. 9 may be reversed. Other configurations and functions are the same as those of the second embodiment.

(Embodiment 4)
The basic structure of the fire detector of the present embodiment is 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, 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, the sound source unit 1 is controlled so that a plurality of types of ultrasonic waves having different frequencies are sequentially transmitted with respect to the first ultrasonic wave transmitted from the first sound source SP1. The relative relationship between the first ultrasonic wave from the sound source SP1 and the second ultrasonic wave from the second sound source SP2 is unchanged. That is, the sound source unit 1 is controlled by the control unit 2 so that the second sound source SP2 always transmits an ultrasonic wave having a second frequency higher than the first ultrasonic wave having the first frequency by a fixed frequency. In other words, the control unit 2 causes the sound source unit to sequentially transmit a plurality of types of combinations of the first ultrasonic wave and the second ultrasonic wave having a fixed frequency higher than the first ultrasonic wave from the sound source unit 1. 1 is controlled.

  In the present embodiment, one sound wave generating element described in the first embodiment is used for each of the first sound source SP1 and the second sound source SP2, and the above-described control unit 2 uses the first sound source SP1 and the second sound source. By sequentially changing the frequency of the drive input waveform applied to SP2, a plurality of types of ultrasonic waves having different frequencies are sequentially transmitted from each of the first sound source SP1 and the second sound source SP2. Here, the control unit 2 changes the frequency of the ultrasonic wave transmitted from the first sound source SP1 from the lower limit frequency (for example, 20 kHz) to the upper limit frequency (for example, 82 kHz) in a predetermined frequency range (for example, 20 kHz to 82 kHz). Let At this time, the supersonic wave from the second sound source SP2 is transmitted so that a frequency (for example, 32 kHz to 94 kHz) higher by a fixed frequency (for example, 12 kHz) than the ultrasonic wave from the first sound source SP1 is transmitted from the second sound source SP2. The frequency of the sound wave is changed from a lower limit frequency (for example, 32 kHz) to an upper limit frequency (for example, 94 kHz). In the present embodiment, the control unit 2 controls the sound source unit 1 so that four types of ultrasonic waves having different frequencies are sequentially transmitted from each of the first sound source SP1 and the second sound source SP2. However, the frequency of the ultrasonic waves transmitted from the sound source unit 1 is not limited to four types, and may be a plurality of types. For example, if two types are used, compared to the case where three or more types of ultrasonic waves are sequentially transmitted. Thus, 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 the present embodiment, as described above, by using the sound wave generating element described in the first embodiment for each of the first sound source SP1 and the second sound source SP2, the ultrasonic waves that are 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 first sound source SP1 and the second sound source SP2, and continuous wave ultrasonic waves are transmitted from each piezoelectric element. I can plan.

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, each of the first sound source SP1 and the second sound source SP2 is configured by a single sound wave generating element, and the frequency of the drive input waveform that the control unit 2 gives to the sound source unit 1 is sequentially changed, Although plural types of ultrasonic waves having different frequencies are sequentially transmitted from the sound source unit 1, the first sound source SP1 and the second sound source SP2 may be configured by a plurality of sound wave generating elements having different output frequencies. Good. 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. It is also conceivable that the sound wave generating element constituting the sound source unit 1 is also used as the wave receiving element 3. In this case, there is a reflection surface that reflects the ultrasonic wave transmitted from the sound wave generating element toward the sound wave generating element. Although necessary, the cost can be reduced by reducing the number of elements.

  Other configurations and functions are the same as those of 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. Further, similarly to the second and third embodiments, a decrease in sound pressure may be suppressed by providing a cylinder.

  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. In this case, the cylindrical body is provided in at least one of the sound source side unit and the wave receiving side unit, or is provided separately from the sound source side unit and the wave receiving side unit. 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. An ultrasonic 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 operation | movement explanatory drawing 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 bottom view which shows the principal part of Embodiment 2 of this invention. It is a schematic bottom view which shows the other example same as the above. It is a schematic perspective view which shows the principal part of Embodiment 3 of this invention. It is a schematic perspective view which shows the other 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 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 Tubular body 11 Base substrate 12 Thermal insulation layer 13 Heating body layer (heating body part)
41 Smoke density estimation means 42 Smoke type judgment means 46 Particle type estimation means 47 Smoke density estimation means 48 Storage means 71 First cylinder 71a Radiation side end face 72 Second cylinder A First ultrasonic wave B Second supersonic wave Sound wave C Beat wave SP1 First sound source SP2 Second sound source

Claims (9)

  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 dense wave transmitted from the sound source unit, and a fire based on the output of the wave 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 value. A first sound source that transmits a first ultrasonic wave having a first frequency higher than a fixed frequency, and a second sound source that transmits a second ultrasonic wave having a second frequency higher than the first frequency by the fixed frequency. The control unit transmits the ultrasonic waves from both the first sound source and the second sound source to the monitoring space at the same time. The sound source unit is controlled to cause the first ultrasonic wave and the second ultrasonic wave to interfere with each other in the monitoring space to generate a beat wave that is a sparse wave of the fixed frequency, and the receiving element receives the beat wave. Fire detector characterized by detecting sound pressure of   The first sound source and the second sound source 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 sound source section and the attenuation amount from the reference value of the output of the receiving element; and the reception of each ultrasonic wave of each frequency transmitted from the sound source section. Particle type estimation means for estimating the type of particles floating in the monitoring space using the output of the element and the relational data stored in the storage means, and the smoke concentration estimation means comprises the particle type estimation The smoke density in the monitoring space is estimated 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 when the particle estimated by the means is a smoke particle. Item 1. Fire detector according to item 1.   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 2.   Each of the first sound source and the second sound source includes a single sound wave generating 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 generating elements. 4. The fire detector according to claim 2, wherein the sound source unit is controlled so as to be waved.   5. The sound source unit according to claim 1, wherein the sound source unit generates an ultrasonic wave by applying a thermal shock to the air due to a temperature change of the heat generating unit accompanying energization of the heat generating unit. The fire detector according to claim 1.   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. 6. The fire detector according to claim 5, further comprising a thermal insulation layer comprising a porous layer that thermally insulates the substrate.   On the propagation path of the ultrasonic wave transmitted from the sound source unit and received by the receiving element, the ultrasonic wave from both the first sound source and the second sound source is formed in an internal space. The fire detector according to any one of claims 1 to 6, wherein a cylindrical body that narrows a diffusion range of the ultrasonic wave by being passed is disposed.   Between the first sound source and the receiving element, one end surface in the longitudinal direction is formed in a cylindrical shape opened as a radiation side end surface, and the ultrasonic wave from the first sound source is passed through the internal space to pass through the ultrasonic wave. A first cylindrical body that narrows the diffusion range of the first sound source is provided, and the second sound source is formed between the second sound source and the receiving element in a cylindrical shape with one end surface in the longitudinal direction opened as a radiation side end surface. A second cylinder that narrows the diffusion range of the ultrasonic wave by passing the ultrasonic wave from the inner space through the internal space, and the first and second cylinders are ultrasonic waves radiated from the respective radiation side end faces. The fire detector according to any one of claims 1 to 6, wherein the fire detectors are disposed so as to interfere with each other in front of the receiving element. Between one of the first sound source and the second sound source and the wave receiving element, one end surface in the longitudinal direction is formed in a cylindrical shape opened as a radiation side end surface, and ultrasonic waves from the one are passed through the internal space. In this way, a cylindrical body that narrows the diffusion range of the ultrasonic waves is provided, and the cylindrical body transmits ultrasonic waves radiated from the end surface on the radiation side from the other of the first sound source and the second sound source. The fire detector according to any one of claims 1 to 6, wherein the fire detector is disposed so as to interfere with the wave receiving element.

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