JP4816526B2 - Fire detector - Google Patents

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JP4816526B2
JP4816526B2 JP2007069092A JP2007069092A JP4816526B2 JP 4816526 B2 JP4816526 B2 JP 4816526B2 JP 2007069092 A JP2007069092 A JP 2007069092A JP 2007069092 A JP2007069092 A JP 2007069092A JP 4816526 B2 JP4816526 B2 JP 4816526B2
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sound source
wave
receiving element
frequency
sound
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JP2008234021A (en
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祥文 渡部
由明 本多
裕司 高田
尚之 西川
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Panasonic Corp
Panasonic Electric Works Co Ltd
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Matsushita Electric Works Ltd
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Priority to CN2007800172608A priority patent/CN101449304B/en
Priority to US12/300,332 priority patent/US8253578B2/en
Priority to EP07742748A priority patent/EP2034462A4/en
Priority to PCT/JP2007/059313 priority patent/WO2007132671A1/en
Priority to TW096116448A priority patent/TWI332643B/en
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Description

本発明は、火災感知器に関するものである。   The present invention relates to a fire detector.

従来から、火災時などに発生する煙を感知する火災感知器として、散乱光式煙感知器（たとえば特許文献１参照）や、減光式煙感知器（たとえば特許文献２参照）が知られている。ここにおいて、散乱光式煙感知器は、発光ダイオード素子よりなる投光素子から監視空間に照射された光の煙粒子による散乱光をフォトダイオードよりなる受光素子で受光するように構成されたものであり、監視空間に煙粒子が存在すれば散乱光が生じることによって受光素子での受光量が増大するから、受光素子での受光量の増加量に基づいて煙粒子の存否を検知できる。一方、減光式煙感知器は、投光素子から照射された光を受光素子により直接受光するように構成されたものであり、投光素子と受光素子との間の監視空間に煙粒子が存在すれば受光素子の受光量が減少するから、受光素子での受光量の減光量に基づいて煙粒子の存否を検知できる。   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.

ところで、散乱光式煙感知器は、迷光対策としてラビリンス体を設ける必要があるので、空気の流れが少ない場合には、火災発生時に監視空間へ煙粒子が侵入するまでの時間が長くなり、応答性に問題があった。また、減光式煙感知器においては、火災が発生していないにもかかわらずバックグランド光の影響で発報してしまう（非火災報が発生してしまう）ことがあるという問題があった。また、分離型の減光式煙感知器は、投光素子と受光素子との光軸を高精度に軸合わせする必要があり、施工に手間がかかるという問題があった。
特開２００１−３４８６２号公報 特開昭６１−３３５９５号公報 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

上述した光電式の火災感知器の問題点を解決するために、本願出願人は、超音波を用いて煙の存否を検知する火災感知器を提案している（図２参照）。   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).

この火災感知器は、超音波を送波可能な音源部１と、音源部１を制御する制御部２と、音源部１から送波された超音波の音圧を検出する受波素子３と、受波素子３の出力に基づいて火災の有無を判別する信号処理部４とを備える。信号処理部４は、受波素子３の出力の基準値からの減衰量に基づいて音源部１と受波素子３との間の監視空間の煙濃度を推定する煙濃度推定手段４１と、推定された煙濃度と所定の閾値とを比較して火災の有無を判断する煙式判断手段４２とを有する。すなわち、監視空間に煙粒子が入り込むと音源部１からの超音波は受波素子３に到達するまでに音圧が低下し、受波素子３の出力の減衰量は監視空間の煙濃度に略比例して増加するので、この減衰量に基づき煙濃度を推定することで、火災の有無を判断することができる。   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.

この超音波式の火災感知器では、光電式の火災感知器で問題となるバックグランド光の影響をなくすことができ、散乱光式煙感知器に必要なラビリンス体を不要とすることができて火災発生時に監視空間へ煙粒子が拡散しやすくなるから、散乱光式煙感知器に比べて応答性を向上でき、また、減光式煙感知器に比べて非火災報の低減が可能になる。   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. .

ところで、上述した超音波式の火災感知器においては、煙濃度の変化量に対する受波素子３の出力の変化量は比較的小さく、ＳＮ比が小さいという問題がある。そこで、音源部１から送波させる超音波の周波数を高くすることが考えられる。超音波の周波数を高くすれば、監視空間の煙濃度が一定でも超音波の音圧の低下量が大きくなり、ＳＮ比の改善につながる。   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.

しかし、一般的な受波素子３（マイクロホン）は高い周波数（たとえば、２００ｋＨｚ）の超音波には対応しておらず、超音波の周波数が高くなるほど感度が低下するので、音源部１から送波させる超音波の周波数を高くしても、受波素子３の感度が低下することにより、結局ＳＮ比は改善されない。   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.

本発明は上記事由に鑑みて為されたものであって、音源部と受波素子との間の監視空間における超音波の減衰量に基づいて火災の有無を判別する構成において、ＳＮ比を向上させた火災感知器を提供することを目的とする。   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.

請求項１の発明では、超音波を送波可能な音源部と、音源部を制御する制御部と、音源部から送波された疎密波の音圧を検出する受波素子と、受波素子の出力に基づいて火災の有無を判断する信号処理部とを備え、信号処理部は、受波素子の出力の基準値からの減衰量に基づいて音源部と受波素子との間の監視空間の煙濃度を推定する煙濃度推定手段と、煙濃度推定手段にて推定された煙濃度と所定の閾値とを比較して火災の有無を判断する煙式判断手段とを有し、音源部は、前記受波素子が感度を有する固定周波数よりも高い第１周波数の第１の超音波を送波する第１音源と、第１周波数よりも前記固定周波数だけ高い第２周波数の第２の超音波を送波する第２音源とを有し、制御部は、第１音源と第２音源との両方から監視空間に超音波を同時に送波させるように音源部を制御することで、監視空間において第１の超音波と第２の超音波とを互いに干渉させて前記固定周波数の疎密波であるビート波を生じさせ、受波素子は前記ビート波の音圧を検出することを特徴とする。   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.

この構成によれば、音源部は、受波素子が感度を有する固定周波数よりも高い第１周波数の第１の超音波を送波する第１音源と、第１周波数よりも前記固定周波数だけ高い第２周波数の第２の超音波を送波する第２音源とを有し、制御部が、第１音源と第２音源との両方から監視空間に超音波を同時に送波させるように音源部を制御することで、監視空間において第１の超音波と第２の超音波とを互いに干渉させて前記固定周波数の疎密波であるビート波を生じさせ、受波素子において前記ビート波の音圧を検出するので、音源部から送波される第１および第２の各超音波の周波数を比較的高く設定しながらも、受波素子で受波するビート波の周波数を比較的低くすることができる。すなわち、音源部から送波させる超音波の周波数を高くすることで監視空間の浮遊粒子による超音波の減衰率を向上させつつ、受波素子で受波させる疎密波の周波数を低くすることにより受波素子の感度を向上させることができ、結果的にＳＮ比が向上するという利点がある。   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.

請求項２の発明は、請求項１の発明において、前記第１音源と前記第２音源とが周波数の異なる複数種の超音波をそれぞれから送波可能であって、前記信号処理部が、前記監視空間に存在する浮遊粒子の種別および煙濃度に応じた前記音源部の出力周波数と前記受波素子の出力の基準値からの減衰量との関係データを記憶した記憶手段と、前記音源部から送波された各周波数の超音波ごとの前記受波素子の出力と記憶手段に記憶されている関係データとを用いて前記監視空間に浮遊している粒子の種別を推定する粒子種別推定手段とを有し、前記煙濃度推定手段が、粒子種別推定手段にて推定された粒子が煙粒子のときに特定周波数の超音波に対する前記受波素子の出力の基準値からの減衰量に基づいて前記監視空間の煙濃度を推定することを特徴とする。   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.

この構成によれば、信号処理部では、粒子種別推定手段において、音源部から送波された各周波数の超音波ごとの受波素子の出力と記憶手段に記憶されている関係データとを用いて監視空間に浮遊している粒子の種別を推定し、粒子種別推定手段にて推定された粒子が煙粒子のときに、煙濃度推定手段において、特定周波数の超音波に対する受波素子の出力の基準値からの減衰量に基づいて監視空間の煙濃度を推定するので、粒子種別識別手段において監視空間に浮遊している粒子の種別を推定することで、たとえば煙粒子と湯気とを識別可能となるから、散乱光式煙感知器および減光式煙感知器に比べて湯気に起因した非火災報を低減することが可能となり、台所や浴室での使用にも適する。   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.

請求項３の発明は、請求項２の発明において、前記記憶手段は、前記関係データとして前記音源部の出力周波数と前記受波素子の出力の基準値からの減衰量を基準値で除した減衰率との関係データを記憶していることを特徴とする。   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.

この発明によれば、前記音源部の出力周波数に応じて前記受波素子の出力の基準値が変動する場合でも、前記音源部の出力周波数と基準値の変動の影響が除去された減衰率との関係データを用いることにより、基準値の変動の影響を受けずに前記監視空間に浮遊している粒子の種別を推定することができる。   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.

請求項４の発明は、請求項２または請求項３の発明において、前記第１音源と前記第２音源とがそれぞれ前記複数種の超音波を送波可能な単一の音波発生素子からなり、前記制御部が各音波発生素子からそれぞれ複数種の超音波が順次送波されるように前記音源部を制御することを特徴とする。   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.

この構成によれば、第１音源と第２音源とのそれぞれに各種の超音波を送波可能な音波発生素子を複数個備える場合に比べて、音源部の小型化、低コスト化が可能となる。   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.

請求項５の発明は、請求項１ないし請求項４のいずれかの発明において、前記音源部が、発熱体部への通電に伴う発熱体部の温度変化により空気に熱衝撃を与えることで超音波を発生するものであることを特徴とする。   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.

この構成によれば、音源部は平坦な周波数特性を有しており、発生させる超音波の周波数を広範囲にわたって変化させることができる。   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.

請求項６の発明は、請求項５の発明において、前記音源部が、ベース基板の一表面側に前記発熱体部が形成されるとともに、ベース基板の前記一表面側で前記発熱体部とベース基板との間に設けられて前記発熱体部とベース基板とを熱絶縁する多孔質層からなる熱絶縁層を有してなることを特徴とする。   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.

この構成によれば、熱絶縁層が多孔質層からなるので、熱絶縁層が非多孔質層からなる場合に比べて、熱絶縁層の断熱性が向上して発熱体部への入力電圧に対する超音波の音圧の比が高くなり、低消費電力化を図ることができる。   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.

請求項７の発明は、請求項１ないし請求項６のいずれかの発明において、前記音源部から送波され前記受波素子で受波される超音波の伝搬経路上には、筒状に形成され前記第１音源と前記第２音源との両方からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める筒体が配設されていることを特徴とする。   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.

この構成によれば、筒状に形成され第１音源と第２音源との両方からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める筒体が、音源部から送波され受波素子で受波される超音波の伝搬経路上に配設されているので、音源部からの超音波は筒体内を通ることで拡散が抑制され、音源部と受波素子との間における超音波の拡散による音圧の低下を抑制することができる。したがって、煙濃度の変化量に対する受波素子の出力の変化量が比較的大きくなり、ＳＮ比が向上する。   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.

請求項８の発明は、請求項１ないし請求項６のいずれかの発明において、前記第１音源と前記受波素子との間には、長手方向の一端面が放射側端面として開口した筒状に形成され前記第１音源からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める第１の筒体が設けられ、前記第２音源と前記受波素子との間には、長手方向の一端面が放射側端面として開口した筒状に形成され前記第２音源からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める第２の筒体が設けられており、第１および第２の筒体がそれぞれの放射側端面から放射される超音波を前記受波素子の手前で互いに干渉させるように配置されていることを特徴とする。   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.

この構成によれば、長手方向の一端面が放射側端面として開口した筒状に形成され第１音源からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める第１の筒体が第１音源と受波素子との間に設けられ、長手方向の一端面が放射側端面として開口した筒状に形成され第２音源からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める第２の筒体が第２音源と受波素子との間に設けられているので、第１音源および第２音源からの各超音波は第１および第２の各筒体内を通ることで拡散が抑制され、音源部と受波素子との間における超音波の拡散による音圧の低下を抑制することができる。しかも、第１および第２の筒体の外側でビート波を生じさせるので、受波素子で受波するビート波の周波数が低い場合にも、各筒体の内周面の粘性抵抗が原因でビート波が減衰してしまうことはない。したがって、煙濃度の変化に対する受波素子の出力の変化量が大きくなり、ＳＮ比が向上する。   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.

請求項９の発明は、請求項１ないし請求項６のいずれかの発明において、前記第１音源および前記第２音源の一方と前記受波素子との間には、長手方向の一端面が放射側端面として開口した筒状に形成され前記一方からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める筒体が設けられており、筒体が放射側端面から放射される超音波を、前記第１音源および前記第２音源の他方から送波される超音波と前記受波素子の手前で干渉させるように配置されていることを特徴とする。   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.

この構成によれば、第１音源および第２音源の一方と受波素子との間には、長手方向の一端面が放射側端面として開口した筒状に形成され一方からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める筒体が設けられているので、前記一方からの超音波は筒体内を通ることで拡散が抑制され、音源部と受波素子との間における超音波の拡散による音圧の低下を抑制することができる。また、第１音源および第２音源の他方から送波される超音波については、筒体を設けたことによる制限を受けることなく周波数を設定することができるので、第１周波数と第２周波数との差に相当する固定周波数を自由に設定することができる。つまり、受波素子での受波感度の高い周波数に、ビート波の周波数を合わせることができる。   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.

本発明は、音源部から送波させる第１および第２の各超音波の周波数の高くすることで監視空間の浮遊粒子による超音波の減衰率を向上させつつ、受波素子で受波させるビート波の周波数を低くすることにより受波素子の感度を向上させることができ、結果的にＳＮ比が向上するという効果がある。   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.

（実施形態１）
本実施形態の火災感知器は、図２に示すように、超音波を送波可能な音源部１と、音源部１を制御する制御部２と、音源部１から送波された疎密波（後述するビート波）の音圧を検出する受波素子３と、受波素子３の出力に基づいて火災の有無を判断する信号処理部４とを備えている。ここにおいて、音源部１と受波素子３とは、図３に示すように、円盤状のプリント基板からなる回路基板５の一表面側において互いに離間して対向配置されており、回路基板５に制御部２および信号処理部４が設けられている。受波素子３の周辺には、音源部１以外で発生した疎密波が受波素子３に入射するのを阻止する遮音板からなる遮音壁６が設けられている。また、回路基板５の上記一表面には、音源部１から送波された超音波の反射を防止する吸音層（図示せず）が設けられているので、音源部１から送波された超音波が回路基板５で反射して受波素子３に入射するのを防止することができて、反射波の干渉を防止することができ、特に、音源部１から送波させる超音波として連続波を用いる場合に有効である。 (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.

本実施形態では、音源部１として、後述のように空気に熱衝撃を与えることで超音波を発生させる音波発生素子を用いることで、圧電素子に比べて残響時間が短い超音波を送波するようにし、且つ、受波素子３として共振特性のＱ値が圧電素子に比べて十分に小さく受波信号に含まれる残響成分の発生期間が短い静電容量型のマイクロホンを用いている。   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.

ここにおいて、音源部１は、図４に示すように、単結晶のｐ形のシリコン基板からなるベース基板１１の一表面（図４における上面）側に多孔質シリコン層からなる熱絶縁層（断熱層）１２が形成され、熱絶縁層１２の表面側に発熱体部として金属薄膜からなる発熱体層１３が形成され、ベース基板１１の上記一表面側に発熱体層１３と電気的に接続された一対のパッド１４，１４が形成されている。なお、ベース基板１１の平面形状は矩形状であって、熱絶縁層１２、発熱体層１３それぞれの平面形状も矩形状に形成してある。また、ベース基板１１の上記一表面側において熱絶縁層１２が形成されていない部分の表面にはシリコン酸化膜からなる絶縁膜（図示せず）が形成されている。   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.

上述の音源部１では、発熱体層１３の両端のパッド１４，１４間に通電して発熱体層１３に急激な温度変化を生じさせると、発熱体層１３に接触している空気（媒質）に急激な温度変化（熱衝撃）が生じる（つまり、発熱体層１３に接触している空気に熱衝撃が与えられる）。したがって、発熱体層１３に接触している空気は、発熱体層１３の温度上昇時には膨張し発熱体層１３の温度下降時には収縮するから、発熱体層１３への通電を適宜に制御することによって空気中を伝搬する超音波を発生させることができる。要するに、音源部１を構成する音波発生素子は、発熱体層１３への通電に伴う発熱体層１３の急激な温度変化を媒質の膨張収縮に変換することにより媒質を伝搬する超音波を発生する。   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. .

上述の音源部１は、ベース基板１１としてｐ形のシリコン基板を用いており、熱絶縁層１２を多孔度が略６０〜略７０％の多孔質シリコン層からなる多孔質層により構成しているので、ベース基板１１として用いるシリコン基板の一部をフッ化水素水溶液とエタノールとの混合液からなる電解液中で陽極酸化処理することにより熱絶縁層１２となる多孔質シリコン層を形成することができる（ここで、陽極酸化処理により形成された多孔質シリコン層は、結晶粒径がナノメータオーダの微結晶シリコンからなるナノ結晶シリコンを多数含んでいる）。多孔質シリコン層は、多孔度が高くなるにつれて熱伝導率および熱容量が小さくなるので、熱絶縁層１２の熱伝導率および熱容量をベース基板１１の熱伝導率および熱容量に比べて小さくし、熱絶縁層１２の熱伝導率と熱容量との積をベース基板１１の熱伝導率と熱容量との積に比べて十分に小さくすることにより、発熱体層１３の温度変化を空気に効率よく伝達することができ発熱体層１３と空気との間で効率的な熱交換が起こり、且つ、ベース基板１１が熱絶縁層１２からの熱を効率よく受け取って熱絶縁層１２の熱を逃がすことができて発熱体層１３からの熱が熱絶縁層１２に蓄積されるのを防止することができる。なお、熱伝導率が１４８Ｗ／（ｍ・Ｋ）、熱容量が１．６３×１０６Ｊ／（ｍ３・Ｋ）の単結晶のシリコン基板を陽極酸化して形成される多孔度が６０％の多孔質シリコン層は、熱伝導率が１Ｗ／（ｍ・Ｋ）、熱容量が０．７×１０６Ｊ／（ｍ３・Ｋ）であることが知られている。本実施形態では、熱絶縁層１２を多孔度が略７０％の多孔質シリコン層により構成してあり、熱絶縁層１２の熱伝導率が０．１２Ｗ／（ｍ・Ｋ）、熱容量が０．５×１０６Ｊ／（ｍ３・Ｋ）となっている。 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).

発熱体層１３は、高融点金属の一種であるタングステンにより形成してあるが、発熱体層１３の材料はタングステンに限らず、たとえば、タンタル、モリブデン、イリジウム、アルミニウムなどを採用してもよい。また、上述の音源部１では、ベース基板１１の厚さを３００〜７００μｍ、熱絶縁層１２の厚さを１〜１０μｍ、発熱体層１３の厚さを２０〜１００ｎｍ、各パッド１４の厚さを０．５μｍとしてあるが、これらの厚さは一例であって特に限定するものではない。また、ベース基板１１の材料としてＳｉを採用しているが、ベース基板１１の材料はＳｉに限らず、たとえば、Ｇｅ、ＳｉＣ、ＧａＰ、ＧａＡｓ、ＩｎＰなどの陽極酸化処理による多孔質化が可能な他の半導体材料でもよく、いずれの場合にも、ベース基板１１の一部を多孔質化することで形成した多孔質層を熱絶縁層１２とすることができる。   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.

上述のように音源部１は、一対のパッド１４，１４を介した発熱体層１３への通電に伴う発熱体層１３の温度変化に伴って超音波を発生するものであり、発熱体層１３へ与える駆動電圧波形あるいは駆動電流波形からなる駆動入力波形をたとえば周波数がｆ１の正弦波波形とした場合、理想的には、発熱体層１３で生じる温度振動の周波数が駆動入力波形の周波数ｆ１の２倍の周波数ｆ２となり、駆動入力波形ｆ１の略２倍の周波数の超音波を発生させることができる。すなわち、上述の音源部１は、圧電素子のように機械的振動により超音波を発生する場合に比べて、平坦な周波数特性を有しており、発生させる超音波の周波数を広範囲にわたって変化させることができる。また、上述の音源部１では、たとえば正弦波波形の半周期の孤立波を駆動入力波形として一対のパッド１４，１４間へ与えることによって、残響の少ない略１周期の単パルス状の超音波を発生させることも可能である。また、音源部１は、熱絶縁層１２が多孔質層により構成されているので、熱絶縁層１２が非多孔質層（たとえば、ＳｉＯ２膜など）からなる場合に比べて、熱絶縁層１２の断熱性が向上して超音波発生効率が高くなり、低消費電力化を図れる。 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.

音源部１を制御する制御部２は、図示していないが、音源部１に駆動入力波形を与えて音源部１を駆動する駆動回路と、当該駆動回路を制御するマイクロコンピュータからなる制御回路とで構成されている。   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

また、上述の受波素子３を構成する静電容量型のマイクロホンは、図５に示すように、シリコン基板に厚み方向に貫通する窓孔３１ａを設けることで形成された矩形枠状のフレーム３１と、フレーム３１の一表面側においてフレーム３１の対向する２つの辺に跨る形で配置されるカンチレバー型の受圧部３２とを備えている。ここにおいて、フレーム３１の一表面側には熱酸化膜３５と熱酸化膜３５を覆うシリコン酸化膜３６とシリコン酸化膜３６を覆うシリコン窒化膜３７とが形成されており、受圧部３２の一端部がシリコン窒化膜３７を介してフレーム３１に支持され、他端部が上記シリコン基板の厚み方向においてシリコン窒化膜３７に対向している。また、シリコン窒化膜３７における受圧部３２の他端部との対向面に金属薄膜（たとえば、クロム膜など）からなる固定電極３３ａが形成され、受圧部３２の他端部におけるシリコン窒化膜３７との対向面とは反対側に金属薄膜（たとえば、クロム膜など）からなる可動電極３３ｂが形成されている。なお、フレーム３１の他表面にはシリコン窒化膜３８が形成されている。また、受圧部３２は、上記各シリコン窒化膜３７，３８とは別工程で形成されるシリコン窒化膜により構成されている。   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.

図５に示した構成の静電容量型のマイクロホンからなる受波素子３では、固定電極３３ａと可動電極３３ｂとを電極とするコンデンサが形成されるから、受圧部３２が疎密波の圧力を受けることにより固定電極３３ａと可動電極３３ｂとの間の距離が変化し、固定電極３３ａと可動電極３３ｂとの間の静電容量が変化する。したがって、固定電極３３ａおよび可動電極３３ｂに設けたパッド（図示せず）間に直流バイアス電圧を印加しておけば、パッドの間には疎密波の音圧に応じて微小な電圧変化が生じるから、疎密波の音圧を電気信号に変換することができる。   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.

ところで、信号処理部４は、受波素子３の出力の基準値からの減衰量に基づいて音源部１と受波素子３との間の監視空間の煙濃度を推定する煙濃度推定手段４１と、煙濃度推定手段４１にて推定された煙濃度と所定の閾値とを比較して火災の有無を判断する煙式判断手段４２と、音源部１が超音波を送波してから当該超音波に相当する疎密波が受波素子３に受波されるまでの時間差に基づいて音速を求める音速検出手段４３と、音速検出手段４３で求めた音速に基づいて上記監視空間の温度を推定する温度推定手段４４と、温度推定手段４４で推定された温度と規定温度とを比較して火災の有無を判断する熱式判断手段４５とを有している。信号処理部４は、マイクロコンピュータにより構成されており、上記各手段４１〜４５は、上記マイクロコンピュータに適宜のプログラムを搭載することにより実現されている。また、信号処理部４は、受波素子３の出力信号をアナログ−ディジタル変換するＡ／Ｄ変換器などが設けられている。   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.

煙濃度推定手段４１は、音源部１からの疎密波の音圧を検出する受波素子３の出力の基準値からの減衰量に基づいて煙濃度を推定するものであるが、音源部１から送波される超音波の周波数が一定であれば、上記減衰量は上記監視空間の煙濃度に略比例して増加するので、あらかじめ測定した煙濃度と減衰量との関係データに基づいて煙濃度と減衰量との関係式を求めて記憶しておけば、上記関係式を用いて減衰量から煙濃度を推定することができる。また、煙式判断手段４２は、煙濃度推定手段４１にて推定された煙濃度が上記閾値未満の場合には「火災無し」と判断する一方で、上記閾値以上の場合には「火災有り」と判断して火災感知信号を制御部２へ出力する。ここで、制御部２は、煙式判断手段４２からの火災感知信号を受信すると、音源部１から可聴域の音波からなる警報音が発生するように音源部１への駆動入力波形を制御する。したがって、音源部１から警報音を発生させることができるので、警報音を出力するスピーカなどを別途に設ける必要がなく、火災感知器全体の小型化および低コスト化が可能となる。   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.

また、音速検出手段４３は、音源部１と受波素子３との間の距離と上記時間差とを用いて音速を求める。また、温度推定手段４４は、周知の大気中の音速と絶対温度との関係式を利用して音速から上記監視空間の温度を推定する。熱式判断手段４５は、温度推定手段４４にて推定された温度が上記規定温度未満の場合には「火災無し」と判断する一方で、上記規定温度以上の場合には「火災有り」と判断して火災感知信号を制御部２へ出力する。ここで、制御部２は、熱式判断手段４５からの火災感知信号を受信した場合にも、音源部１から可聴域の音波からなる警報音が発生するように音源部１への駆動入力波形を制御する。なお、音速検出手段４３は、煙濃度を推定するために音源部１から送波させる超音波とは別に、所定周波数の疎密波を定期的に送波させ当該疎密波が受波素子３に受波されるまでの時間差に基づいて音速を求めるようにしてもよいし、煙濃度を推定するために音源部１から送波させる超音波を用いて音速を求めるようにしてもよい。   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.

ところで、音源部１から送波される超音波の周波数を高くすれば、監視空間の煙濃度が一定でも超音波の音圧の低下量が大きくなり、ＳＮ比の改善につながるので、本実施形態では、音源部１から送波させる超音波の周波数を比較的高く設定してある。ただし、一般的な受波素子３は高い周波数（たとえば、２００ｋＨｚ）の超音波には対応しておらず、超音波の周波数が高くなるほど感度が低下するという問題があるので、本実施形態では以下の構成を採用することによりこの問題を解決している。   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.

すなわち、本実施形態の音源部１は、図１（ａ）に示すように第１周波数の超音波（以下、第１の超音波ともいう）を送波する第１音源ＳＰ１と、図１（ｂ）に示すように第１周波数よりも高い第２周波数の超音波（以下、第２の超音波ともいう）を送波する第２音源ＳＰ２とを有している。第１音源ＳＰ１および第２音源ＳＰ２はいずれも受波素子３に対向する形で同一面に並設される。ここで、第２周波数は第１周波数よりも所定の固定周波数だけ高く設定されており、固定周波数は少なくとも第１周波数よりも低く設定されている。さらに、制御部２は、第１音源ＳＰ１と第２音源ＳＰ２との両方から監視空間に超音波を同時に送波させるように第１音源ＳＰ１および第２音源ＳＰ２を制御する。これより、第１音源ＳＰ１と第２音源ＳＰ２との各々から送波された超音波は、監視空間の媒質（空気）の非線形性によって互いに干渉し、図１（ｃ）のように両超音波の周波数の差に相当する周波数（固定周波数）を有した疎密波であるビート波を発生する。なお、図１中の「Ａ」，「Ｂ」はそれぞれ第１の超音波、第２の超音波を表し、「Ｃ」はビート波を表している。つまり、監視空間においては、第１の超音波（図１（ａ）の「Ａ」）と第２の超音波（図１（ｂ）の「Ｂ」）とが１次波として入射されると、第２周波数と第１周波数との差である固定周波数のビート波（図１（ｃ）の「Ｃ」）が２次波として発生する。   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.

一方、受波素子３としては上述した固定周波数の疎密波に対して十分な感度を有するものを採用しており、受波素子３は、第１音源ＳＰ１や第２音源ＳＰ２の各々から送波された超音波そのものの音圧を検出するのではなく、上記ビート波の音圧を検出する。したがって、本実施形態の構成によれば、音源部１から送波させる第１および第２の各超音波の周波数（つまり第１周波数、第２周波数）を比較的高く設定しながらも、受波素子で受波するビート波の周波数（つまり固定周波数）を低く設定することができる。   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.

以下に、本実施形態の具体例を挙げる。音速ｃが３４０ｍ／ｓ、音源部１と受波素子３との間の距離Ｌが３４ｍｍのとき、第１音源ＳＰ１から送波させる第１の超音波の周波数を２００ｋＨｚに設定し、第２音源ＳＰ２から送波させる第２の超音波の周波数を２２０ｋＨｚに設定する。ここで、制御部２はたとえば１００周期程度ずつの超音波を第１音源ＳＰ１および第２音源ＳＰ２からそれぞれ連続的に送波させるように音源部１を制御する。この場合、監視空間においては、第１周波数（＝２００ｋＨｚ）と第２周波数（＝２２０ｋＨｚ）との差である固定周波数（＝２０ｋＨｚ）のビート波が発生する。したがって、受波素子３においては２０ｋＨｚの疎密波の音圧を検出することになり、一般的な受波素子３（上述した静電容量型のマイクロホンに限らず、たとえばエレクトレットコンデンサマイクなども含む）でも十分な感度で音圧の検出が可能である。ここにおいて、音源部１から送波される超音波は２００ｋＨｚおよび２２０ｋＨｚであるから、監視空間に煙粒子があれば２００ｋＨｚ相当の周波数の超音波と同等の音圧低下が生じ、受波素子３の出力の減衰量は比較的大きくなる。   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.

なお、本実施形態では、煙式判断手段４２や熱式判断手段４５から出力される火災感知器信号を制御部２へ出力するようにしているが、制御部２に限らず、たとえば、外部の通報装置へ出力するようにしてもよい。   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.

また、本実施形態では、第１音源ＳＰ１と第２音源ＳＰ２とを同一面に並べて音源部１を構成し、音源部１と監視空間を介して対向する形で受波素子３を配置した例を示したが、第１音源ＳＰ１と第２音源ＳＰ２とを監視空間を介して互いに対向させる形で配置し、監視空間における第１音源ＳＰ１と第２音源ＳＰ２との対向方向の中央部に受波素子３を配置するようにしてもよい。   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.

以上説明した本実施形態の火災感知器では、煙濃度推定手段４１において、受波素子３の出力の基準値からの減衰量に基づいて音源部１と受波素子３との間の監視空間の煙濃度を推定し、煙式判断手段４２において、煙濃度推定手段４１にて推定された煙濃度と所定の閾値とを比較して火災の有無を判断するので、散乱光式煙感知器や減光式煙感知器のような光電式の火災感知器で問題となるバックグランド光の影響をなくすことができ、散乱光式煙感知器に必要なラビリンス体を不要とすることができて火災発生時に監視空間へ煙粒子が拡散しやすくなるから、散乱光式煙感知器に比べて応答性を向上でき、さらに、減光式煙感知器に比べて非火災報の低減が可能になる。   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.

また、本実施形態では、音源部１が第１周波数の超音波を送波する第１音源ＳＰ１と、第２周波数の超音波を送波する第２音源ＳＰ２とを有し、制御部２が第１音源ＳＰ１と第２音源ＳＰ２との両方から監視空間に超音波を同時に送波させるように音源部１を制御することでビート波を生じさせ、受波素子３が前記ビート波の音圧を検出するようにしたので、音源部１から送波される各超音波の周波数（つまり第１周波数および第２周波数）を比較的高く設定しながらも、受波素子３で受波するビート波の周波数（つまり固定周波数）を比較的低く設定することができる。したがって、音源部１から送波される各超音波の周波数を比較的高くすることで監視空間の煙粒子による超音波の音圧の低下量を増加させつつ、受波素子３で受波する疎密波の周波数を低くすることで一般的な受波素子３でも十分な感度で音圧を検出することができ、結果的にＳＮ比が向上するという利点がある。   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.

さらに、本実施形態の火災感知器では、音速検出手段４３において、音源部１が超音波を送波してから疎密波が受波素子３に受波されるまでの時間差に基づいて音速を求め、温度推定手段４４において、音速検出手段４３で求めた音速に基づいて上記監視空間の温度を推定し、熱式判断手段４５において、温度推定手段４４で推定された温度と規定温度とを比較して火災の有無を判断するので、別途に温度検出素子を用いることなく火災発生時の温度上昇によっても火災を感知することが可能となり、火災をより確実に感知することが可能になる。   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.

（実施形態２）
本実施形態の火災感知器は、基本構成が実施形態１と略同じであり、図６に示すように筒状に形成された筒体７を音源部１と受波素子３との間に配設した点が実施形態１の火災感知器と相違する。なお、実施形態１と同様の構成要素には同一の符号を付して説明を適宜省略する。 (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.

筒体７は、長手方向の両端面が閉塞された直管状の角筒であって、図６に示すように長手方向の一端面（図６における左端面）に音源部１（つまり第１音源ＳＰ１および第２音源ＳＰ２）が配置されるとともに、他端面（図６における右端面）に受波素子３が配置されており、内部空間を通して音源部１からの超音波を伝搬させる。この筒体７を設けたことにより、音源部１から送波される超音波は、筒体７の内部空間を通ることで拡散が抑制され、したがって音源部１と受波素子３との間における超音波の拡散による音圧の低下を抑制することができる。なお、この構成では筒体７内が監視空間となるので、たとえば筒体７の長手方向に沿う側面には内部に煙等を案内する孔（図示せず）が形成される。   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.

さらに、本実施形態では、筒体７は長手方向の両端面が閉じられた周知の音響管と同様に、固有の共振周波数を有する。つまり、筒体７の長手方向の寸法をＬとするときに、Ｌ＝（ｎ／２）×λの関係（ただし、ｎは自然数）を満たす波長λに対応する周波数ｆ（波の伝搬速度をｃとしてｆ＝ｃ／λで表される）が筒体７の共振周波数となる。したがって、Ｌ＝（ｎ／２）×λの関係を満たす超音波の連続波が長手方向の端面から筒体７内に入射すると、当該超音波の少なくとも一部が筒体７の長手方向の両端面で反射を繰り返すことにより、反射波と音源部１からの直接波とが重なって共振し、筒体７の内部において前記超音波の音圧が増大する。そこで、本実施形態は制御部２において、筒体７に固有の前記共振周波数の超音波を第１音源ＳＰ１および第２音源ＳＰ２から送波させるように音源部１を制御することにより、筒体７内で共振を生じさせ音源部１からの超音波の音圧を増大させるようにしてある。この場合、筒体７内で共振を生じさせるために、Ｌ／λを超える複数周期（以下、ｍ周期という）の超音波を音源部１から送波させる必要があるので、制御部２は、ｍ（＞Ｌ／λ）周期の超音波の連続波を音源部１から送波させるように音源部１を制御する。言い換えると、音源部１から超音波を連続して送波させる送波時間ｔｐ（つまりｔｐ＝ｍ×λ／ｃ）が、筒体７の長手方向の両端間を超音波が伝搬するのに要する伝搬時間ｔｓ（つまりｔｓ＝Ｌ／ｃ）よりも大きくなる（つまりｔｐ＞ｔｓ）ように制御部２で音源部１を制御する。受波素子３は、筒体７内で共振が発生して超音波の音圧が飽和したタイミングでビート波の音圧を検出する。通常、音源部１からの超音波の送波が終了した時点で超音波の音圧が飽和するので、一例として音源部１からの超音波の送波を終了するのと同時に受波素子３においてビート波の音圧を検出することが考えられる。 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.

以下に、本実施形態の具体例を挙げる。音速ｃが３４０ｍ／ｓ、筒体７の長手方向の寸法Ｌが３４ｍｍのとき、Ｌ＝（ｎ／２）×λの関係を満たすには、第１音源ＳＰ１から送波させる第１の超音波の周波数（＝ｃ／λ）を２００ｋＨｚ（ｎ＝４０）に設定し、第２音源ＳＰ２から送波させる第２の超音波の周波数を２２０ｋＨｚ（ｎ＝４４）に設定すればよい。ここで、上述したようにｍ（＞Ｌ／λ）周期の超音波の連続波を音源部１から送波させるように音源部１を制御する必要があるので、制御部２はたとえば１００周期程度ずつの超音波を第１音源ＳＰ１および第２音源ＳＰ２からそれぞれ連続的に送波させるように音源部１を制御する。この場合、監視空間においては、第１周波数（＝２００ｋＨｚ）と第２周波数（＝２２０ｋＨｚ）との差である固定周波数（＝２０ｋＨｚ）のビート波が発生する。したがって、受波素子３においては２０ｋＨｚの疎密波の音圧を検出することになり、一般的な受波素子３でも十分な感度で音圧の検出が可能である。ここにおいて、音源部１から送波される超音波は２００ｋＨｚおよび２２０ｋＨｚであるから、監視空間に煙粒子があれば２００ｋＨｚ相当の周波数の超音波と同等の音圧低下が生じ、受波素子３の出力の減衰量は比較的大きくなる。   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.

なお、本実施形態では、筒体７の長手方向の一端面に第１音源ＳＰ１と第２音源ＳＰ２とを並べて配置し、筒体７の長手方向の他端面に受波素子３を配置した例を示したが、図７に示すように第１音源ＳＰ１と第２音源ＳＰ２とを筒体７の長手方向の各端面にそれぞれ配置し、筒体７の長手方向に沿う側面における中央部に受波素子３を配置するようにしてもよい。   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.

以上説明した本実施形態の火災感知器では、音源部１と受波素子３との間の超音波の伝搬経路に筒体７を設けたことにより、音源部１から送波される超音波は、筒体７の内部空間を通ることで拡散が抑制され、音源部１と受波素子３との間における超音波の拡散による音圧の低下を抑制することができるので、監視空間中に煙粒子がない状態において受波素子３で受波されるビート波の音圧を高く維持でき、煙濃度の変化量に対する受波素子３の出力の変化量が比較的大きくなり、その結果、ＳＮ比が向上するという効果がある。   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.

また、本実施形態では、筒体７内で共振を生じさせ音源部１からの超音波の音圧を増大させているので、音源部１と受波素子３との間における音圧の低下をより一層抑制することができ、煙濃度の変化量に対する受波素子３の出力の変化量が大きくなってＳＮ比が一層向上する。しかも、共振により筒体７の長手方向の端面で反射を繰り返す超音波においては、実効的な送波距離が反射の回数に応じて延長され、実質、超音波は筒体７の長手方向の寸法Ｌの数倍の送波距離を経て受波素子３に到達する。このことも煙濃度の変化量に対する受波素子３の出力の変化量の増大に寄与しており、非共振の単パルス状の超音波が受波素子３で受波される場合に比較して超音波の減衰量は数倍に増大する。   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.

なお、その他の構成および機能は実施形態１と同様である。   Other configurations and functions are the same as those in the first embodiment.

（実施形態３）
本実施形態の火災感知器は、基本構成が実施形態２と略同じであり、筒体の構成が実施形態２の火災感知器と相違する。なお、実施形態２と同様の構成要素には同一の符号を付して説明を適宜省略する。 (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.

本実施形態では筒体として、図８に示すように長手方向の一端面が放射側端面７１ａとして開口し長手方向の他端面が第１音源ＳＰ１で覆われた第１の筒体７１と、長手方向の一端面が放射側端面（図示せず）として開口し長手方向の他端面が第２音源ＳＰ２で覆われた第２の筒体７２とを用いている。両筒体７１，７２はそれぞれの放射側端面７１ａ（開口面）を受波素子３に向け、両放射側端面７１ａから放射される超音波が受波素子３の手前（受波素子３と放射側端面７１ａとの間）で互いに干渉するようにＶ字状に配置されている。これにより、第１音源ＳＰ１および第２音源ＳＰ２からそれぞれ送波される超音波は、各筒体７１，７２を通して放射側端面７１ａから放射され、受波素子３の手前で互いに交差することで媒質（空気）の非線形性によって互いに干渉してビート波を生じる。   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.

また、本実施形態では各筒体７１，７２の長手方向の一端面が開口しているので、各筒体７１，７２はそれぞれ長手方向の一端面が閉じられた周知の音響管と同様に、固有の共振周波数を有する。つまり、筒体７１，７２の長手方向の寸法をＬとするときに、Ｌ＝（１／４＋ｎ／２）×λの関係（ただし、ｎ＝０，１，２，３，…）を満たす波長λに対応する周波数ｆ（＝ｃ／λ）が筒体７１，７２の共振周波数となる。したがって、Ｌ＝（１／４＋ｎ／２）×λの関係を満たす超音波の連続波が長手方向の端面から筒体７１，７２内に入射すると、当該超音波の少なくとも一部が筒体７１，７２の長手方向の両端面で反射を繰り返すことにより、反射波と音源部１からの直接波とが重なって共振し、筒体７１，７２の内部において前記超音波の音圧が増大する。そこで、制御部２において、筒体７１，７２に固有の前記共振周波数の超音波が第１音源ＳＰ１および第２音源ＳＰ２から送波されるように音源部１を制御すれば、筒体７１，７２内で共振を生じさせ音源部１からの超音波の音圧を増大させることができる。この場合、筒体７１，７２内で共振を生じさせるために、制御部２は、ｍ（＞Ｌ／λ）周期の超音波の連続波を音源部１から送波させるように音源部１を制御する。言い換えると、音源部１から超音波を連続して送波させる送波時間ｔｐ（＝ｍ×λ／ｃ）が、筒体７１，７２の長手方向の両端間を超音波が伝搬するのに要する伝搬時間ｔｓ（＝Ｌ／ｃ）よりも大きくなる（つまりｔｐ＞ｔｓ）ように制御部２で音源部１を制御する。なお、一方の端面を開口端とする場合、周知のように開口端よりも僅かΔＬだけ外側に、超音波の音圧の節（つまり空気の移動速度の腹）が生じるので、共振周波数を求める際に用いる長さＬを上記ΔＬだけ補正（開口端の補正）すれば、より正確な共振周波数を求めることができる。 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.

以下に、本実施形態の具体例を挙げる。音速ｃが３４０ｍ／ｓ、各筒体７１，７２の長手方向の寸法Ｌが３４ｍｍのとき、Ｌ＝（１／４＋ｎ／２）×λの関係を満たすには、第１音源ＳＰ１から送波させる第１の超音波の周波数を２０２．５ｋＨｚ（ｎ＝４０）に設定し、第２音源ＳＰ２から送波させる第２の超音波の周波数を２２２．５ｋＨｚ（ｎ＝４４）に設定すればよい。ここで、上述したようにｍ（＞Ｌ／λ）周期の超音波の連続波を音源部１から送波させるように音源部１を制御する必要があるので、制御部２はたとえば１００周期程度ずつの超音波を第１音源ＳＰ１および第２音源ＳＰ２からそれぞれ連続的に送波させるように音源部１を制御する。この場合、監視空間においては、第１周波数（＝２０２．５ｋＨｚ）と第２周波数（＝２２２．５ｋＨｚ）との差である固定周波数（＝２０ｋＨｚ）のビート波が発生する。したがって、受波素子３においては２０ｋＨｚの疎密波の音圧を検出することになり、一般的な受波素子３でも十分な感度で音圧の検出が可能である。ここにおいて、音源部１から送波される超音波は２０２．５ｋＨｚおよび２２２．５ｋＨｚであるから、監視空間に煙粒子があれば２００ｋＨｚ相当の周波数の超音波と同等の音圧低下が生じ、受波素子３の出力の減衰量は比較的大きくなる。   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.

以上説明した本実施形態の構成によれば、第１および第２の各筒体７１，７２の外側でビート波を生じさせるので、受波素子３で受波するビート波の周波数が低い場合にも、各筒体７１，７２の内周面の粘性抵抗が原因でビート波が減衰してしまうことはない。すなわち、筒体７１,７２の断面積（管径）が小さい場合には、疎密波が筒体７１，７２中を通る際に筒体７１，７２の内周面の粘性抵抗により、ある周波数以下の疎密波の音圧が低下することがあるが、本実施形態の構成では、筒体７１，７２内を通る疎密波においては音圧が低下しないように高い周波数（つまり第１周波数および第２周波数）に設定することができる。したがって、煙濃度の変化に対する受波素子３の出力の変化量が大きくなり、ＳＮ比が向上する。   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.

また、本実施形態では第１音源ＳＰ１と第２音源ＳＰ２とのそれぞれに筒体７１，７２を設ける例を示したが、図９に示すように第１音源ＳＰ１からの超音波を通す第１の筒体７１のみを設けるようにし、当該筒体７１の放射側端面７１ａから放射される超音波と第２音源ＳＰ２から送波される超音波とを、受波素子３の手前で干渉させるようにしてもよい。図９の例では、第１の筒体７１の放射側端面７１ａと受波素子３との間に向けて、側方から第２音源ＳＰ２が超音波を放射するように、第１音源ＳＰ１と第２音源ＳＰ２と筒体７１と受波素子３とが配置されている。この構成では、第２音源ＳＰ２から送波される超音波については、筒体７１を設けたことによる制限を受けることなく周波数を設定することができるので、第１周波数と第２周波数との差に相当する固定周波数を自由に設定することができる。つまり、受波素子３での受波感度が最も高い周波数に、ビート波の周波数を合わせることができる。   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.

以下に図９の構成における具体例を挙げる。音速ｃが３４０ｍ／ｓ、筒体７１の長手方向の寸法Ｌが３４ｍｍのとき、Ｌ＝（１／４＋ｎ／２）×λの関係を満たすには、第１音源ＳＰ１から送波させる第１の超音波の周波数を２０２．５ｋＨｚ（ｎ＝４０）に設定すればよい。一方、第２音源ＳＰ２から送波させる第２の超音波の周波数においては、筒体７１の共振周波数に合わせる必要はないので、受波素子３における感度の周波数特性に基づいて設定することが望ましい。つまり、受波素子３の感度がたとえば１２ｋＨｚの疎密波に対して最大となる場合、第２周波数を第１周波数（＝２０２．５ｋＨｚ）よりも１２ｋＨｚ高い２１４．５ｋＨｚに設定することが望ましい。この場合、監視空間においては、第１周波数（＝２０２．５ｋＨｚ）と第２周波数（＝２１４．５ｋＨｚ）との差である固定周波数（＝１２ｋＨｚ）のビート波が発生する。したがって、受波素子３においては１２ｋＨｚの疎密波の音圧を検出することになり、感度が最大となる周波数で動作させることができる。   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.

なお、図９の構成で第１音源ＳＰ１と第２音源ＳＰ２との関係は逆であってもよい。その他の構成および機能は実施形態２と同様である。   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.

（実施形態４）
本実施形態の火災感知器は、基本構成が実施形態１と略同じであり、図１０に示すように制御部２および信号処理部４の構成が相違する。なお、実施形態１と同様の構成要素には同一の符号を付して説明を適宜省略する。 (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.

ところで、本願発明者らは、音源部１と受波素子３との間の監視空間の浮遊粒子の種別に応じて図１１に示すように音源部１の出力周波数と音圧の単位減衰率との関係が異なるという知見を得た。ここで、監視空間に浮遊粒子が存在しない状態で受波素子３にて受波される音圧（以下、基準音圧という）をＩ０、減光式煙濃度計（減光式煙感知器）での評価でｘ％／ｍとなる濃度の浮遊粒子が監視空間に存在する状態で受波素子３にて受波される音圧をＩｘとしたときに、（Ｉ０−Ｉｘ）／Ｉ０で表される値を音圧の減衰率と定義し、特にｘ＝１のときの減衰率を単位減衰率と定義する。ここにおいて、基準音圧Ｉ０と音圧Ｉｘとは、監視空間における浮遊粒子の有無を除いては同一の条件で検出されるものとする。図１１中の「イ」は浮遊粒子が黒煙の煙粒子である場合の出力周波数と音圧の単位減衰率との関係を示す近似曲線（黒丸が測定データ）、「ロ」は浮遊粒子が白煙の煙粒子である場合の出力周波数と音圧の単位減衰率との関係を示す近似曲線（黒四角が測定データ）、「ハ」は浮遊粒子が湯気の粒子である場合の出力周波数と音圧の単位減衰率との関係を示す近似曲線（黒三角が測定データ）であり、ここに示す単位減衰率は、音源部１と受波素子３との間の距離を３０ｃｍに設定したときの各出力周波数ごとのデータである。また、図１１における右端の各データは、出力周波数が８２ｋＨｚのときのデータであり、出力周波数が８２ｋＨｚのときのデータを１として各出力周波数の単位減衰率を規格化した結果を図１２に示す。要するに、図１２は、横軸が出力周波数、縦軸が相対的単位減衰率となっている。また、白煙の煙粒子のサイズは８００ｎｍ程度、黒煙の煙粒子のサイズは２００ｎｍ程度、湯気の粒子のサイズは数μｍ〜２０μｍ程度である。 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.

上述の知見に基づいて、本実施形態では、制御部２が、音源部１から周波数の異なる複数種の超音波が順次送波されるように音源部１を制御するようにし、信号処理部４は、少なくとも受波素子３の基準出力（基準音圧に対する受波素子３の出力）、上記監視空間に存在する浮遊粒子の種別および浮遊粒子濃度に応じた音源部１の出力周波数と受波素子３の出力の相対的単位減衰率との関係データ（上述の図１２より抽出されるデータ）、煙粒子に関して特定周波数（たとえば、８２ｋＨｚ）における単位減衰率（上述の図１１より抽出されるデータ）を記憶した記憶手段４８と、音源部１から送波された各周波数の超音波ごとの受波素子３の出力と記憶手段４８に記憶されている関係データとを用いて上記監視空間に浮遊している粒子の種別を推定する粒子種別推定手段４６と、粒子種別推定手段４６にて推定された粒子が煙粒子のときに特定周波数（たとえば、８２ｋＨｚ）の超音波に対する受波素子３の出力の基準値からの減衰量に基づいて上記監視空間の煙濃度を推定する煙濃度推定手段４７と、煙濃度推定手段４７にて推定された煙濃度と所定の閾値とを比較して火災の有無を判断する煙式判断手段４２とを有するようにしてある。   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.

以下に、本実施形態の火災感知器の動作例を図１３のフローチャートを参照して説明する。まず、音源部１から複数種の超音波を順次送波させ各超音波に対する受波素子３の出力を信号処理部４で計測する（ステップＳ１１）。粒子種別推定手段４６は、各出力周波数ごとに受波素子３の出力と記憶手段４８に記憶されている基準出力とから音圧の減衰率を求め（ステップＳ１２）、出力周波数が８２ｋＨｚでの音圧の減衰率に対する２０ｋＨｚでの音圧の減衰率の比を算出する（ステップＳ１３）。記憶手段４８には、音源部１の出力周波数と受波素子３の出力の相対的単位減衰率との上記関係データとして、出力周波数が８２ｋＨｚでの相対的単位減衰率に対する２０ｋＨｚでの相対的単位減衰率の比（図１２の場合、白煙が０、黒煙が０．２、湯気が０．５となる）が記憶されており、粒子種別推定手段４６は、算出した減衰率の比を記憶手段４８に記憶されている関係データと比較し、関係データの中で減衰率の比が最も近い種別の粒子を監視空間に浮遊している粒子と推定する（ステップＳ１４）。ここで、推定された粒子が煙粒子であれば煙濃度推定手段４７での処理に移行する（ステップＳ１５）。ここにおいて、白煙の場合には図１４に示すように減光式煙濃度計で計測される煙濃度と音圧の減衰率との関係は直線で示すことのできるデータであり、他の粒子においても同様であるから、煙濃度推定手段４７は、推定された粒子種別について特定周波数（たとえば、８２ｋＨｚ）の超音波に対する受波素子３の出力の減衰率の記憶手段４８に記憶されている単位減衰率に対する比を算出し、その比の値がｙの場合に監視空間の煙濃度が減光式煙濃度計での評価における煙濃度ｙ％／ｍに相当すると推定する（ステップＳ１６）。煙式判断手段４２は、ステップＳ１６で推定された煙濃度と所定の閾値（たとえば、減光式煙濃度計での評価で１０％／ｍとなる煙濃度）とを比較し、推定された煙濃度が上記閾値未満の場合には「火災無し」と判断する一方で、上記閾値以上の場合には「火災有り」と判断して火災感知信号を制御部２へ出力する。   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.

上述の例では、粒子種別推定手段４６は出力周波数が８２ｋＨｚのときの減衰率と２０ｋＨｚのときの減衰率とを用いているが、これらの出力周波数の組み合わせに限定するものではなく、異なる組み合わせの出力周波数を用いてもよい。さらに、より多くの出力周波数に対する減衰率を用いてもよく、その場合は粒子種別の推定の確度を向上させることができる。また、本実施形態では、煙濃度推定手段４７が特定周波数として１周波数を対象としているが、特定周波数として複数の周波数を対象とし、各特定周波数ごとに推定した煙濃度の平均値を求めるようにしてもよく、この場合、煙濃度の推定の確度が向上する。なお、信号処理部４は、マイクロコンピュータにより構成されており、粒子種別推定手段４６、煙濃度推定手段４７、煙式判断手段４２は、上記マイクロコンピュータに適宜のプログラムを搭載することにより実現されている。また、信号処理部４は、受波素子３の出力信号をアナログ−ディジタル変換するＡ／Ｄ変換器などが設けられている。   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.

また、本実施形態では第１音源ＳＰ１から送波させる第１の超音波について、周波数の異なる複数種の超音波が順次送波されるように音源部１を制御するようにしており、第１音源ＳＰ１からの第１の超音波と第２音源ＳＰ２からの第２の超音波との相対的な関係は不変としている。すなわち、第２音源ＳＰ２からは、常に第１周波数の第１の超音波よりも固定周波数だけ高い第２周波数の超音波が送波されるように制御部２で音源部１を制御する。言い換えれば、制御部２は、第１の超音波と第１の超音波よりも固定周波数だけ高い第２の超音波との複数種の組み合わせを、音源部１から順次送波させるように音源部１を制御する。   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.

本実施形態では、第１音源ＳＰ１、第２音源ＳＰ２のそれぞれに実施形態１にて説明した音波発生素子を１つずつ用いており、上述の制御部２は、第１音源ＳＰ１および第２音源ＳＰ２へ与える駆動入力波形の周波数を順次変化させることにより、第１音源ＳＰ１および第２音源ＳＰ２の各々から周波数の異なる複数種の超音波を順次送波させる。ここにおいて、制御部２は、第１音源ＳＰ１から送波させる超音波の周波数を所定の周波数範囲（たとえば、２０ｋＨｚ〜８２ｋＨｚ）の下限周波数（たとえば、２０ｋＨｚ）から上限周波数（たとえば、８２ｋＨｚ）まで変化させる。このとき、第１音源ＳＰ１からの超音波よりも固定周波数（たとえば、１２ｋＨｚ）だけ高い周波数（たとえば、３２ｋＨｚ〜９４ｋＨｚ）が第２音源ＳＰ２から送波されるように、第２音源ＳＰ２からの超音波の周波数を下限周波数（たとえば、３２ｋＨｚ）から上限周波数（たとえば、９４ｋＨｚ）まで変化させる。なお、本実施形態では、第１音源ＳＰ１と第２音源ＳＰ２との各々から周波数の異なる４種類の超音波が順次送波されるように制御部２が音源部１を制御するように構成してあるが、音源部１から送波させる超音波の周波数は４種類に限らず複数種類であればよく、たとえば、２種類とすれば、３種類以上の超音波を順次送波させる場合に比べて、制御部２および信号処理部４の負担を軽減できるとともに制御部２および信号処理部４の簡略化を図れる。本実施形態では、上述のように第１音源ＳＰ１、第２音源ＳＰ２の各々に実施形態１にて説明した音波発生素子を用いることで、順次送波する超音波をそれぞれ周波数の異なる超音波とすることができるので、第１音源ＳＰ１、第２音源ＳＰ２の各々に共振周波数の異なる複数の圧電素子を用いて各圧電素子から連続波の超音波を送波させる場合に比べて低コスト化を図れる。   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.

なお、本実施形態では、音源部１の出力周波数と受波素子３の出力の相対的単位減衰率との関係データを記憶手段４８に記憶した例を示したが、そもそも監視空間に存在する浮遊粒子の種別に応じて音源部１の出力周波数ごとに変化するのは受波素子３の出力の基準値からの減衰量（Ｉ０−Ｉｘ）であるから、記憶手段４８に記憶する上記関係データは、音源部１の出力周波数と受波素子３の出力の基準値からの減衰量との関係を示すデータであればよく、上述の相対的単位減衰率に代えて、たとえば、受波素子３の出力の基準値からの減衰量や、受波素子３の出力の基準値からの減衰量を基準値（Ｉ０）で除しただけの減衰率、あるいは単位減衰率を採用した関係データを記憶手段４８に記憶するようにしてもよい。 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.

以上説明した本実施形態の火災感知器では、粒子種別推定手段４６において、音源部１から送波された各周波数の超音波ごとの受波素子３の出力と記憶手段４８に記憶されている関係データとを用いて上記監視空間に浮遊している粒子の種別を推定し、粒子種別推定手段４６にて推定された粒子が煙粒子のときに、煙濃度推定手段４７において、特定周波数の超音波に対する受波素子３の出力の基準値からの減衰量に基づいて上記監視空間の煙濃度を推定し、煙式判断手段４２において、煙濃度推定手段４７にて推定された煙濃度と所定の閾値とを比較して火災の有無を判断するので、散乱光式煙感知器や減光式煙感知器のような光電式の火災感知器で問題となるバックグランド光の影響をなくすことができ、散乱光式煙感知器に必要なラビリンス体を不要とすることができて散乱光式煙感知器に比べて応答性を向上でき、また、減光式煙感知器に比べて非火災報の低減が可能になる。しかも、粒子種別推定手段４６において上記監視空間に浮遊している粒子の種別を推定することで煙粒子と湯気とを識別可能となるから、散乱光式煙感知器および減光式煙感知器に比べて湯気に起因した非火災報を低減することが可能となり、台所や浴室での使用にも適する。また、粒子種別推定手段４６において白煙の煙粒子と黒煙の煙粒子とを識別可能となるから、火災の性状の識別に役立てることも可能となる。また、火災感知器を設置している室内の掃除や天井裏の電気工事などの際に浮遊する粉塵と煙粒子との識別も可能になるから、粉塵などに起因した非火災報を低減することも可能となる。   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.

ところで、本実施形態では第１音源ＳＰ１と第２音源ＳＰ２との各々を単一の音波発生素子により構成し、制御部２が音源部１へ与える駆動入力波形の周波数を順次変化させることにより、音源部１から周波数の異なる複数種の超音波を順次送波させるようにしているが、互いに出力周波数の異なる複数の音波発生素子で第１音源ＳＰ１と第２音源ＳＰ２とをそれぞれ構成してもよい。この場合には、各音波発生素子として圧電素子のように機械的振動により超音波を発生する素子を用い、各音波発生素子をそれぞれの共振周波数で駆動することにより、音源部１から送波される超音波の音圧を高めてＳＮ比の向上に寄与することができる。また、音源部１を構成する音波発生素子を受波素子３に兼用することも考えられ、この場合、音波発生素子から送波される超音波を当該音波発生素子に向けて反射する反射面が必要であるものの、素子数の低減による低コスト化を図ることができる。   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.

なお、その他の構成および機能は実施形態１と同様であり、たとえば本実施形態の火災感知器においても、図２に示した実施形態１と同様、信号処理部４に、音速検出手段４３、温度推定手段４４、熱式判断手段４５を設けてもよい。また、実施形態２、３と同様に、筒体を設けて音圧の低下を抑制してもよい。   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.

ところで、上記各実施形態では、音源部１と制御部２と受波素子３と信号処理部４とを１枚の回路基板５に設けて図示しない器体内に収納してあるが、音源部１と制御部２とを備えた音源側ユニットと、受波素子３と信号処理部４とを備えた受波側ユニットとを別体として互いに対向配置する分離型の火災報知機を構成するようにしてもよい。この場合、筒体は音源側ユニットと受波側ユニットとの少なくとも一方に設けられるか、あるいは音源側ユニットおよび受波側ユニットとは別に設けられる。また、音源部１は上述の図３に示した構成の音波発生素子に限らず、たとえば、アルミニウム製の薄板を発熱体部として当該発熱体部への通電に伴う発熱体部の急激な温度変化による熱衝撃によって超音波を発生させるものでもよい。   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.

さらにまた、信号処理部４は、定期的に、所定周波数（たとえば、上述の特定周波数と同じ８２ｋＨｚ）の超音波に対する受波素子３の出力に基づいて、音源部１の出力変動や受波素子３の感度変動がキャンセルされるように制御部２による音源部１の制御条件と受波素子３の出力の信号処理条件との少なくとも一方を変更するようにすれば、音源部１の出力変動や受波素子３の感度変動を定期的にキャンセルすることが可能となり、長期的な信頼性が高くなる。   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.

また、上記各実施形態において、制御部２が、音源部１から防虫効果のある周波数の超音波を送波させるようにすれば、上記監視空間に虫が侵入するのを防止することができ、虫に起因した非火災報を低減できる。ここで、制御部２は、煙濃度を推定するために音源部１から送波させる周波数の超音波とは別に、防虫効果のある周波数の超音波を定期的に送波させるようにしてもよいし、煙濃度を推定するために音源部１から送波する超音波の周波数を防虫効果のある周波数に設定するようにしてもよい。   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.

本発明の実施形態１の動作説明図である。It is operation | movement explanatory drawing of Embodiment 1 of this invention. 同上の構成を示すブロック図である。It is a block diagram which shows a structure same as the above. 同上の要部を示し、（ａ）は概略下面図、（ｂ）は概略側面図である。The principal part same as the above is shown, (a) is a schematic bottom view, (b) is a schematic side view. 同上に用いる音波発生素子を示す概略断面図である。It is a schematic sectional drawing which shows the sound wave generation element used for the same as the above. 同上に用いる受波素子を示し、（ａ）は一部破断した概略斜面図、（ｂ）は概略断面図である。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. 本発明の実施形態２の要部を示す概略下面図である。It is a schematic bottom view which shows the principal part of Embodiment 2 of this invention. 同上の他の例を示す概略下面図である。It is a schematic bottom view which shows the other example same as the above. 本発明の実施形態３の要部を示す概略斜視図である。It is a schematic perspective view which shows the principal part of Embodiment 3 of this invention. 同上の他の例を示す概略斜視図である。It is a schematic perspective view which shows the other example same as the above. 本発明の実施形態４の構成を示すブロック図である。It is a block diagram which shows the structure of Embodiment 4 of this invention. 同上の音源部の出力周波数と音圧の単位減衰率との関係を示す説明図である。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. 同上の音源部の出力周波数と相対的単位減衰率との関係を示す説明図である。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. 同上の動作例を示すフローチャートである。It is a flowchart which shows the operation example same as the above. 同上の煙濃度と特定周波数の超音波の減衰率との関係を示す説明図である。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.

符号の説明Explanation of symbols

１ 音源部
２ 制御部
３ 受波素子
４ 信号処理部
７ 筒体
１１ ベース基板
１２ 熱絶縁層
１３ 発熱体層（発熱体部）
４１ 煙濃度推定手段
４２ 煙式判断手段
４６ 粒子種別推定手段
４７ 煙濃度推定手段
４８ 記憶手段
７１ 第１の筒体
７１ａ 放射側端面
７２ 第２の筒体
Ａ 第１の超音波
Ｂ 第２の超音波
Ｃ ビート波
ＳＰ１ 第１音源
ＳＰ２ 第２音源
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)

超音波を送波可能な音源部と、音源部を制御する制御部と、音源部から送波された疎密波の音圧を検出する受波素子と、受波素子の出力に基づいて火災の有無を判断する信号処理部とを備え、信号処理部は、受波素子の出力の基準値からの減衰量に基づいて音源部と受波素子との間の監視空間の煙濃度を推定する煙濃度推定手段と、煙濃度推定手段にて推定された煙濃度と所定の閾値とを比較して火災の有無を判断する煙式判断手段とを有し、音源部は、前記受波素子が感度を有する固定周波数よりも高い第１周波数の第１の超音波を送波する第１音源と、第１周波数よりも前記固定周波数だけ高い第２周波数の第２の超音波を送波する第２音源とを有し、制御部は、第１音源と第２音源との両方から監視空間に超音波を同時に送波させるように音源部を制御することで、監視空間において第１の超音波と第２の超音波とを互いに干渉させて前記固定周波数の疎密波であるビート波を生じさせ、受波素子は前記ビート波の音圧を検出することを特徴とする火災感知器。   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 前記第１音源と前記第２音源とは周波数の異なる複数種の超音波をそれぞれから送波可能であって、前記信号処理部は、前記監視空間に存在する浮遊粒子の種別および煙濃度に応じた前記音源部の出力周波数と前記受波素子の出力の基準値からの減衰量との関係データを記憶した記憶手段と、前記音源部から送波された各周波数の超音波ごとの前記受波素子の出力と記憶手段に記憶されている関係データとを用いて前記監視空間に浮遊している粒子の種別を推定する粒子種別推定手段とを有し、前記煙濃度推定手段は、粒子種別推定手段にて推定された粒子が煙粒子のときに特定周波数の超音波に対する前記受波素子の出力の基準値からの減衰量に基づいて前記監視空間の煙濃度を推定することを特徴とする請求項１記載の火災感知器。   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. 前記記憶手段は、前記関係データとして前記音源部の出力周波数と前記受波素子の出力の基準値からの減衰量を基準値で除した減衰率との関係データを記憶していることを特徴とする請求項２記載の火災感知器。   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. 前記第１音源と前記第２音源とはそれぞれ前記複数種の超音波を送波可能な単一の音波発生素子からなり、前記制御部は各音波発生素子からそれぞれ複数種の超音波が順次送波されるように前記音源部を制御することを特徴とする請求項２または請求項３記載の火災感知器。   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. 前記音源部は、発熱体部への通電に伴う発熱体部の温度変化により空気に熱衝撃を与えることで超音波を発生するものであることを特徴とする請求項１ないし請求項４のいずれか１項に記載の火災感知器。   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. 前記音源部は、ベース基板の一表面側に前記発熱体部が形成されるとともに、ベース基板の前記一表面側で前記発熱体部とベース基板との間に設けられて前記発熱体部とベース基板とを熱絶縁する多孔質層からなる熱絶縁層を有してなることを特徴とする請求項５記載の火災感知器。   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. 前記音源部から送波され前記受波素子で受波される超音波の伝搬経路上には、筒状に形成され前記第１音源と前記第２音源との両方からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める筒体が配設されていることを特徴とする請求項１ないし請求項６のいずれか１項に記載の火災感知器。   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. 前記第１音源と前記受波素子との間には、長手方向の一端面が放射側端面として開口した筒状に形成され前記第１音源からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める第１の筒体が設けられ、前記第２音源と前記受波素子との間には、長手方向の一端面が放射側端面として開口した筒状に形成され前記第２音源からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める第２の筒体が設けられており、第１および第２の筒体はそれぞれの放射側端面から放射される超音波を前記受波素子の手前で互いに干渉させるように配置されていることを特徴とする請求項１ないし請求項６のいずれか１項に記載の火災感知器。   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. 前記第１音源および前記第２音源の一方と前記受波素子との間には、長手方向の一端面が放射側端面として開口した筒状に形成され前記一方からの超音波を内部空間に通すことで当該超音波の拡散範囲を狭める筒体が設けられており、筒体は放射側端面から放射される超音波を、前記第１音源および前記第２音源の他方から送波される超音波と前記受波素子の手前で干渉させるように配置されていることを特徴とする請求項１ないし請求項６のいずれか１項に記載の火災感知器。
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.
JP2007069092A 2006-05-12 2007-03-16 Fire detector Expired - Fee Related JP4816526B2 (en)

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JP2007069092A JP4816526B2 (en) 2007-03-16 2007-03-16 Fire detector
CN2007800172608A CN101449304B (en) 2006-05-12 2007-05-01 Smoke sensor of acoustic wave type
US12/300,332 US8253578B2 (en) 2006-05-12 2007-05-01 Smoke sensor of the sound wave type including a smoke density estimation unit
EP07742748A EP2034462A4 (en) 2006-05-12 2007-05-01 Smoke sensor of acoustic wave type
PCT/JP2007/059313 WO2007132671A1 (en) 2006-05-12 2007-05-01 Smoke sensor of acoustic wave type
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