JP5965261B2 - Particle sensor - Google Patents

Particle sensor Download PDF

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JP5965261B2
JP5965261B2 JP2012200130A JP2012200130A JP5965261B2 JP 5965261 B2 JP5965261 B2 JP 5965261B2 JP 2012200130 A JP2012200130 A JP 2012200130A JP 2012200130 A JP2012200130 A JP 2012200130A JP 5965261 B2 JP5965261 B2 JP 5965261B2
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electrodes
exhaust gas
concentration
high voltage
temperature
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JP2014055822A (en
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吉弘 川田
吉弘 川田
佐藤　聡
聡 佐藤
水野　彰
彰 水野
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Hino Motors Ltd
Toyohashi University of Technology NUC
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Toyohashi University of Technology NUC
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本発明は、粒子センサに関するものである。   The present invention relates to a particle sensor.

ディーゼルエンジンから排出されるＰＭ（Particulate Matter：粒子状物質）は、炭素質から成る煤分と、高沸点炭化水素成分から成るＳＯＦ分（Soluble Organic Fraction：可溶性有機成分）とを主成分とし、更に微量のサルフェート（ミスト状硫酸成分）を含んだ組成を成すものであるが、この種のパティキュレートの低減対策としては、排気ガスが流通する排気管の途中に、パティキュレートフィルタを装備することが従来より行われている。   PM (Particulate Matter) discharged from a diesel engine is mainly composed of a soot component composed of carbonaceous matter and a SOF component (Soluble Organic Fraction) composed of high-boiling hydrocarbon components. The composition contains a small amount of sulfate (mist-like sulfuric acid component). As a measure to reduce this type of particulates, a particulate filter is installed in the middle of the exhaust pipe through which the exhaust gas flows. It has been done conventionally.

一方、近年においては、車両の排ガス対策システムにおける故障発生の有無を監視し、故障発生時には警告灯等を点灯させて運転者に故障の発生を報知すると共に、故障内容を記録しておく車載式故障診断装置（オンボードダイアグノーシス：onboard diagnosis:略称ＯＢＤ）の装備が各国で義務付けられており、パティキュレートフィルタの出側で排気ガス中のＰＭ濃度を検出してパティキュレートフィルタに性能不良が生じていないかどうかを監視し得るようにすることが研究されているが、本発明者らは、パティキュレートフィルタの入側でも排気ガス中のＰＭ濃度を検出してエンジン状態を監視し得るようにすることを検討するに到った。   On the other hand, in recent years, on-vehicle type that monitors the occurrence of failure in the exhaust gas countermeasure system of the vehicle, lights up a warning light etc. when the failure occurs, notifies the driver of the occurrence of the failure, and records the failure content A failure diagnosis device (onboard diagnosis: OBD) is required in each country, and PM concentration in exhaust gas is detected on the outlet side of the particulate filter, resulting in poor performance of the particulate filter. Although the present inventors have been studying whether or not it is possible to monitor whether or not the exhaust gas has not been detected, the present inventors have been able to detect the PM concentration in the exhaust gas even at the inlet side of the particulate filter so as to monitor the engine state. I came to consider doing that.

尚、本発明に関連する先行技術文献情報としては下記の特許文献１、２等がある。   The prior art document information related to the present invention includes the following patent documents 1 and 2 and the like.

実開昭６４−５０３５５号公報Japanese Utility Model Publication No. 64-50355 特開２００７−３２７９３６号公報JP 2007-327936 A

しかしながら、現状においては、実験用の測定器として、ＰＭの粒子数（量）を重量、電荷量、光透過（光散乱）等の物理量を検出して濃度とするものが既に存在しているものの、これらは所定量のサンプルを採取してバッチ式に測定を行う形式のものばかりであり、時々刻々変化するＰＭの濃度を連続的に検出することが可能な車載の粒子センサとして供し得るようなものではなかった。   However, under the present circumstances, there are some experimental measuring instruments that measure the number of PM particles (amount) by detecting physical quantities such as weight, charge amount, light transmission (light scattering), and the like to obtain a concentration. These are the ones that take a predetermined amount of sample and perform batch measurement, and can be used as an in-vehicle particle sensor that can continuously detect the concentration of PM that changes every moment. It was not a thing.

このため、時々刻々変化するＰＭの濃度を連続的に検出することが可能な車載の粒子センサの開発が望まれており、先の特許文献１、２等といった粒子センサの提案も成されてはいるが、ＰＭを多く含む排気ガスの流れに晒されながら前記ＰＭの堆積による悪影響を受けずに正確な測定を長期間に亘り継続できる粒子センサは未だ実用化に到っていないのが実情である。   For this reason, development of an in-vehicle particle sensor capable of continuously detecting the concentration of PM that changes every moment is desired, and proposals of particle sensors such as the above-mentioned Patent Documents 1 and 2 have been made. However, particle sensors that can continue accurate measurement for a long period of time without being adversely affected by PM accumulation while being exposed to a flow of exhaust gas containing a large amount of PM have not yet been put into practical use. is there.

本発明は上述の実情に鑑みてなしたもので、時々刻々変化するＰＭの濃度を連続的に検出し且つＰＭの堆積による悪影響を受けずに正確な測定を長期間に亘り継続し得る粒子センサを提供することを目的とする。   The present invention has been made in view of the above circumstances, and is a particle sensor that can continuously detect the concentration of PM that changes every moment and can continue accurate measurement over a long period of time without being adversely affected by PM deposition. The purpose is to provide.

本発明は、排気管を流れる排気ガス中に含まれるＰＭの濃度を検出する粒子センサであって、排気管の途中に排気ガスの流れを横切るように挿入され且つ該排気ガスの流れの向きに並ばないように互いに平行を成して対向配置された円柱形状の一対の電極と、該電極の一方を高電圧電極とし且つ他方を接地電極として両電極間に部分放電が発生するよう矩形波の交流高電圧を印加するパルス高電圧発生手段と、該パルス高電圧発生手段により両電極間に交流高電圧を印加するための電気回路中に介装されたコンデンサと、該コンデンサの端子電圧を測定する電圧測定手段と、該電圧測定手段により測定された電圧値をＰＭ濃度に換算する演算手段とを備えたことを特徴とするものである。   The present invention is a particle sensor for detecting the concentration of PM contained in exhaust gas flowing through an exhaust pipe, and is inserted in the middle of the exhaust pipe so as to cross the flow of exhaust gas and in the direction of the flow of the exhaust gas. A pair of cylindrical electrodes arranged in parallel and facing each other so as not to line up, and one of the electrodes is a high voltage electrode and the other is a ground electrode, and a rectangular wave is generated so that partial discharge occurs between the electrodes. Pulse high voltage generating means for applying an AC high voltage, a capacitor interposed in an electric circuit for applying an AC high voltage between both electrodes by the pulse high voltage generating means, and measuring the terminal voltage of the capacitor Voltage measuring means, and a calculating means for converting the voltage value measured by the voltage measuring means into a PM concentration.

このようにした場合、パルス高電圧発生手段により両電極間に矩形波の交流高電圧を印加すると、該電極間に部分放電が発生してＰＭが帯電し、その帯電したＰＭが電極の夫々に付着することになるが、このＰＭの付着により電極間のギャップが縮まり且つ相互の対向面の表面積が増える結果、部分放電や漏れ電流により電極間の空間や壁面を移動する電荷が増えることでコンデンサに蓄積される電荷量が増加する一方、両電極から成るセンサー部分の静電容量が増えることでもコンデンサに蓄積される電荷量が増加し、斯かる電荷量の増加に伴いコンデンサの端子電圧が上昇するので、その電圧値を電圧測定手段により測定して演算手段で換算することでＰＭ濃度を検出することが可能となる。   In this case, when a rectangular AC high voltage is applied between the electrodes by the pulse high voltage generating means, a partial discharge occurs between the electrodes and the PM is charged, and the charged PM is applied to each of the electrodes. Capacitors are attached, but the gap between the electrodes is reduced due to the adhesion of the PM, and the surface area of the opposing surfaces is increased. As a result, the electric charge that moves through the space and the wall surface between the electrodes due to partial discharge and leakage current increases. While the amount of charge stored in the capacitor increases, the amount of charge stored in the capacitor also increases as the capacitance of the sensor part consisting of both electrodes increases, and the terminal voltage of the capacitor increases as the amount of charge increases. Therefore, it is possible to detect the PM concentration by measuring the voltage value with the voltage measuring means and converting with the calculating means.

更に、コンデンサに蓄積された電荷は、矩形波の交流高電圧の印加により電界の極性が反転して起こるコンデンサの放電によりリセットされる形となり、また、各電極に付着していたＰＭについても、前記電界の極性の反転により電極側と同じ電荷となって反発することで剥離し、排気ガスの流れによりＰＭが吹き飛ばされてリセットされる形となり、その後で新たな電界により帯電したＰＭが付着し始めることになる。   Furthermore, the charge accumulated in the capacitor is reset by the discharge of the capacitor that occurs when the polarity of the electric field is reversed by the application of a rectangular wave AC high voltage, and the PM adhering to each electrode is also Due to the reversal of the polarity of the electric field, it peels off by repelling the same charge as the electrode side, and PM is blown off by the flow of exhaust gas and reset, and then the charged PM is attached by a new electric field. Will start.

ここで、前記各電極は排気ガスの流れに対し平面を持たない円柱形状となっており、しかも、排気管の途中に排気ガスの流れを横切るように挿入され且つ排気ガスの流れの向きに並ばないように対向配置されているので、特に前記各電極の対向面は、排気ガスが接線方向に近い向きから強く吹き付けてＰＭが留まり難い環境が作り出され、電界の極性の反転に伴うＰＭの分離除去が確実に行われることになる。   Here, each of the electrodes has a cylindrical shape having no plane with respect to the flow of the exhaust gas, and is inserted in the middle of the exhaust pipe so as to cross the flow of the exhaust gas, and arranged in the direction of the flow of the exhaust gas. Since the exhaust gas is blown strongly from the direction close to the tangential direction, an environment in which PM does not stay is created, and the separation of the PM accompanying the reversal of the polarity of the electric field is created. Removal will be ensured.

尚、パルス高電圧発生手段により交流高電圧の矩形波の周波数を下げて一周期当たりのコンデンサの充電時間を長くすれば、排気ガス中に含まれるＰＭの濃度が低い場合にも各電極へのＰＭの付着量を有意差がある量としてＰＭ濃度の検出を実現することが可能となる。   If the frequency of the AC high voltage rectangular wave is lowered by the pulse high voltage generating means to increase the charging time of the capacitor per cycle, even when the concentration of PM contained in the exhaust gas is low, It becomes possible to realize the detection of the PM concentration by setting the amount of adhesion of PM as an amount having a significant difference.

また、本発明においては、排気管内の排気ガスの温度を検出する温度センサを更に備え、該温度センサに測定された排気温度に基づき演算手段で算出したＰＭ濃度に温度補正をかけ且つ所定の下限温度以上でのみＰＭ濃度の検出を実施し得るよう構成することが好ましい。   The present invention further includes a temperature sensor that detects the temperature of the exhaust gas in the exhaust pipe, applies temperature correction to the PM concentration calculated by the calculation means based on the exhaust temperature measured by the temperature sensor, and has a predetermined lower limit. It is preferable that the PM concentration can be detected only at the temperature or higher.

このようにすれば、排気温度による電圧値の変動を加味して、より精度の高いＰＭ濃度を求めることが可能となり、しかも、所定の下限温度を下まわるような排気温度の低い結露環境下での不正確な検出を回避することが可能となる。   In this way, it becomes possible to obtain a more accurate PM concentration in consideration of the fluctuation of the voltage value due to the exhaust temperature, and in a dew condensation environment with a low exhaust temperature that falls below a predetermined lower limit temperature. It is possible to avoid inaccurate detection.

更に、本発明をより具体的に実施するに際しては、一対の電極のうちの一方をワイヤで構成し且つ他方を前記ワイヤを支持するためのサポート材を兼ねたロッドで構成することが好ましく、このようにすれば、サポート材を別途設置する必要がなくなって製作が容易となり、サポート材が不要となる分だけ排気ガスの流れに対する圧力損失も少なくて済む。   Furthermore, when carrying out the present invention more specifically, it is preferable that one of the pair of electrodes is composed of a wire and the other is composed of a rod that also serves as a support material for supporting the wire. By doing so, it is not necessary to separately install a support material, and the manufacture becomes easy, and the pressure loss with respect to the flow of exhaust gas can be reduced as much as the support material becomes unnecessary.

上記した本発明の粒子センサによれば、下記の如き種々の優れた効果を奏し得る。   According to the particle sensor of the present invention described above, various excellent effects as described below can be obtained.

（Ｉ）本発明の請求項１に記載の発明によれば、電極の形状と配置を工夫し且つ該各電極に矩形波の交流高電圧をパルス高電圧発生手段で印加することでＰＭの付着と剥離を確実に行わしめて、時々刻々変化するＰＭの濃度を連続的に検出することができ、しかも、ＰＭの堆積による悪影響を受けずに正確な測定を長期間に亘り継続することができ、更には、パルス高電圧発生手段で交流高電圧の矩形波の周波数を下げて一周期当たりのコンデンサの充電時間を長くすることにより、排気ガス中に含まれるＰＭの濃度が低い場合であっても、各電極へのＰＭの付着量を有意差がある量としてＰＭ濃度の検出を実現することができる。   (I) According to the invention described in claim 1 of the present invention, PM is adhered by devising the shape and arrangement of the electrodes and applying a rectangular wave AC high voltage to each of the electrodes by the pulse high voltage generating means. It is possible to detect the concentration of PM continuously changing from time to time, and to continue accurate measurement over a long period without being adversely affected by PM deposition. Furthermore, even if the concentration of PM contained in the exhaust gas is low by lowering the frequency of the rectangular wave of the alternating high voltage with the pulse high voltage generating means to increase the charging time of the capacitor per cycle. The PM concentration can be detected with the amount of PM adhering to each electrode as an amount having a significant difference.

（ＩＩ）本発明の請求項２に記載の発明によれば、排気温度による電圧値の変動を加味した精度の高いＰＭ濃度を求めることができると共に、所定の下限温度を下まわるような排気温度の低い結露環境下での不正確な検出を回避することができる。   (II) According to the invention described in claim 2 of the present invention, it is possible to obtain a highly accurate PM concentration taking into account fluctuations in the voltage value depending on the exhaust gas temperature, and an exhaust gas temperature that falls below a predetermined lower limit temperature. Inaccurate detection under low condensation conditions can be avoided.

（ＩＩＩ）本発明の請求項３に記載の発明によれば、サポート材を不要として製作を容易化することができ、しかも、サポート材が不要となる分だけ排気ガスの流れに対する圧力損失を低減することができる。   (III) According to the invention described in claim 3 of the present invention, it is possible to facilitate the manufacture without using the support material, and to reduce the pressure loss with respect to the flow of the exhaust gas by the amount that the support material is unnecessary. can do.

本発明を実施する形態の一例を示す概略図である。It is the schematic which shows an example of the form which implements this invention. 図１のＩＩ−ＩＩ方向の矢視図である。It is an arrow view of the II-II direction of FIG. 図２の要部を拡大して示す断面図である。It is sectional drawing which expands and shows the principal part of FIG. 本形態例の粒子センサの電気回路図である。It is an electric circuit diagram of the particle sensor of this embodiment. 両電極への印加電圧と電圧測定器の検出電圧を示すグラフである。It is a graph which shows the applied voltage to both electrodes, and the detection voltage of a voltage measuring device. ＰＭの付着と剥離の様子を模式的に示す説明図である。It is explanatory drawing which shows typically the mode of adhesion and peeling of PM.

以下本発明の実施の形態を図面を参照しつつ説明する。   Embodiments of the present invention will be described below with reference to the drawings.

図１は本発明を実施する形態の一例を示すもので、図中１はエンジンからの排気ガス２が流れる排気管を示しており、排気管１の途中に排気ガス２の流れを横切るように一対の電極３，４が挿入されているが、ここに図示している例では、一対の電極３，４のうちの一方を直径約０．２ｍｍ程度のステンレス製のワイヤで構成し且つ他方を前記ワイヤを支持するためのサポート材を兼ねた直径約５ｍｍ程度のステンレス製のロッドで構成している。   FIG. 1 shows an example of an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes an exhaust pipe through which exhaust gas 2 from an engine flows, so that the flow of the exhaust gas 2 crosses in the middle of the exhaust pipe 1. Although a pair of electrodes 3 and 4 are inserted, in the example shown here, one of the pair of electrodes 3 and 4 is made of a stainless steel wire having a diameter of about 0.2 mm and the other is It is composed of a stainless steel rod having a diameter of about 5 mm that also serves as a support material for supporting the wire.

ここで、前記各電極３，４は、互いに平行を成して対向配置された円柱形状を成すようになっており、一対のワイヤで構成することも可能であるが、その場合にはサポート材を別途設けなければならないため、本形態例の場合はワイヤとロッドの組み合わせ例としている。   Here, each of the electrodes 3 and 4 has a columnar shape arranged in parallel and facing each other, and can be constituted by a pair of wires. In this embodiment, a combination of a wire and a rod is used.

また、図１では、説明の便宜上から各電極３，４を排気ガス２の流れ方向に並べた図示となっているが、実際には、図２に図１のＩＩ−ＩＩ方向の矢視図で示している通り、前記各電極３，４を排気ガス２の流れを横切るように並べ、該排気ガス２の流れの向きには並ばないようにする必要がある。   1 shows the electrodes 3 and 4 arranged in the flow direction of the exhaust gas 2 for convenience of explanation, but in actuality, FIG. 2 is a view in the direction of the arrow II-II in FIG. It is necessary to arrange the electrodes 3 and 4 so as to cross the flow of the exhaust gas 2 so that they do not line up in the direction of the flow of the exhaust gas 2.

この際、前記各電極３，４は、排気管１の半径方向に向け中心部近くまで挿し入れて排気ガス２の主流に晒されるようにしておくことが好ましく、このように排気ガス２の主流を検出対象とした方が、排気管１の内壁近くの流れを検出対象とするよりもＰＭ濃度の検出が正確なものとなる。   At this time, each of the electrodes 3 and 4 is preferably inserted to the vicinity of the central portion in the radial direction of the exhaust pipe 1 so as to be exposed to the main flow of the exhaust gas 2. The detection of PM concentration is more accurate than the detection target of the flow near the inner wall of the exhaust pipe 1.

図３は前記各電極３，４の詳細な構造を拡大図で示したものであり、ワイヤで構成された一方の電極３の上下端が、ロッドで構成されている他方の電極４の上下端に装着された絶縁体５，６により支持されるようにしてあり、両者間に約５ｍｍ程度の間隔ｗが確保されるようにしてある。   FIG. 3 shows the detailed structure of each of the electrodes 3 and 4 in an enlarged view. The upper and lower ends of one electrode 3 formed of a wire are the upper and lower ends of the other electrode 4 formed of a rod. It is designed to be supported by insulators 5 and 6 attached to each other, and an interval w of about 5 mm is secured between them.

そして、先の図１に示してある通り、ワイヤで構成された一方の電極３は、車載のバッテリ７（直流電源）に対しスイッチング回路８と昇圧回路９とを介して接続された高電圧電極を成し、ロッドで構成されている他方の電極４は、コンデンサ１０を介し接地されて接地電極を成すようになっており、前述のバッテリ７とスイッチング回路８と昇圧回路９とから成るパルス高電圧発生手段１１により矩形波の交流高電圧が印加されて両電極３，４間に部分放電が発生されるようにしてある。尚、バッテリ７とスイッチング回路８と昇圧回路９とを１台のパルスジェネレータに置き換えてパルス高電圧発生手段１１を構成させることも可能である。   As shown in FIG. 1, the one electrode 3 made of wire is a high-voltage electrode connected to an in-vehicle battery 7 (DC power supply) via a switching circuit 8 and a booster circuit 9. The other electrode 4 composed of a rod is grounded via a capacitor 10 to form a ground electrode, and the pulse height comprising the battery 7, the switching circuit 8 and the booster circuit 9 is described above. A rectangular wave AC high voltage is applied by the voltage generating means 11 to generate a partial discharge between the electrodes 3 and 4. It is also possible to replace the battery 7, the switching circuit 8 and the booster circuit 9 with a single pulse generator to constitute the pulse high voltage generating means 11.

また、前記コンデンサ１０の端子電圧が電圧測定器１２により測定するようになっており、その測定された電圧値が制御装置１３（演算手段）に信号入力されてＰＭ濃度に換算されるようになっている。   Further, the terminal voltage of the capacitor 10 is measured by the voltage measuring device 12, and the measured voltage value is input to the control device 13 (calculation means) and converted into the PM concentration. ing.

ここで、特に本形態例においては、各電極３，４の配置位置に近い排気管１の適宜位置に温度センサ１４が備えられ、該温度センサ１４に測定された排気温度が前記制御装置１３に信号入力されるようになっており、該制御装置１３でＰＭ濃度に温度補正がかけられ且つ所定の下限温度（約１００℃程度）以上でのみＰＭ濃度の検出が実施されるようにしてある。   Here, particularly in the present embodiment, a temperature sensor 14 is provided at an appropriate position of the exhaust pipe 1 close to the position where the electrodes 3 and 4 are arranged, and the exhaust temperature measured by the temperature sensor 14 is supplied to the control device 13. A signal is input, and the control device 13 corrects the temperature of the PM concentration, and the PM concentration is detected only at a predetermined lower limit temperature (about 100 ° C.) or higher.

而して、このように粒子センサを構成した場合、パルス高電圧発生手段１１により両電極３，４間に矩形波の交流高電圧を印加すると、該電極３，４間に部分放電が発生してＰＭが帯電し、その帯電したＰＭが電極３，４の夫々に付着することになるが、このＰＭの付着により電極３，４間のギャップが縮まり且つ相互の対向面の表面積が増える結果、部分放電や漏れ電流により電極３，４間の空間や壁面を移動する電荷が増えることでコンデンサ１０に蓄積される電荷量が増加する一方、両電極３，４から成るセンサー部分の静電容量が増えることでもコンデンサ１０に蓄積される電荷量が増加し、斯かる電荷量の増加に伴いコンデンサ１０の端子電圧が上昇するので、その電圧値を電圧測定器１２により測定して制御装置１３で換算することでＰＭ濃度を検出することが可能となる。   Thus, in the case where the particle sensor is configured in this way, a partial discharge is generated between the electrodes 3 and 4 when the pulsed high voltage generator 11 applies a rectangular wave AC high voltage between the electrodes 3 and 4. PM is charged, and the charged PM adheres to each of the electrodes 3 and 4. As a result of the adhesion of this PM, the gap between the electrodes 3 and 4 is reduced and the surface areas of the opposing surfaces are increased. While the amount of charge moving in the space between the electrodes 3 and 4 and the wall surface due to partial discharge and leakage current increases, the amount of charge accumulated in the capacitor 10 increases, while the capacitance of the sensor portion comprising both electrodes 3 and 4 increases. Increasing the charge also increases the amount of charge accumulated in the capacitor 10, and the terminal voltage of the capacitor 10 increases as the amount of charge increases. The voltage value is measured by the voltage measuring device 12 and converted by the control device 13. Do It becomes possible to detect PM concentration in the.

ここで、両電極３，４から成るセンサー部分の静電容量が増えることでコンデンサ１０に蓄積される電荷量が増加する理由につき補足して説明すると、本形態例の粒子センサは、図４の如き電気回路として図示することができ、電極３，４から成るセンサー部分をコンデンサのように見立てた場合、その静電容量は、下記の式（１）のように表すことができる。
［数１］
Ｃ＝εＳ／ｄ…（１）
Ｃ：静電容量
ε：誘電率
Ｓ：電極の対向面の表面積
ｄ：電極間のギャップ Here, the reason why the amount of electric charge accumulated in the capacitor 10 increases as the capacitance of the sensor portion composed of both electrodes 3 and 4 increases will be described. The particle sensor of this embodiment is shown in FIG. When the sensor portion composed of the electrodes 3 and 4 is regarded like a capacitor, the capacitance can be expressed as the following equation (1).
[Equation 1]
C = εS / d (1)
C: Capacitance ε: Dielectric constant S: Surface area of the opposing surface of the electrode d: Gap between the electrodes

依って、ＰＭの付着により電極３，４間のギャップｄが縮まり且つ相互の対向面の表面積Ｓが増えれば、電極３，４から成るセンサー部分の静電容量Ｃは増えることになる。   Therefore, if the gap d between the electrodes 3 and 4 is reduced due to the adhesion of PM and the surface area S of the opposing surfaces is increased, the capacitance C of the sensor portion composed of the electrodes 3 and 4 increases.

そして、電荷量Ｑ、静電容量Ｃ、印加電圧Ｖの間には、下記の式（２）のような関係がある。
［数２］
Ｑ＝ＣＶ…（２） And there exists a relationship like the following formula | equation (2) among the electric charge Q, the electrostatic capacitance C, and the applied voltage V. FIG.
[Equation 2]
Q = CV (2)

このため、決められた印加電圧Ｖに対し静電容量Ｃが増えれば、電極３，４から成るセンサー部分における電荷量Ｑが増えることになり、コンデンサ１０における電荷量も増えることになるが、コンデンサ１０における静電容量は不変であるため、コンデンサ１０の端子電圧が増加することになる。   Therefore, if the capacitance C increases with respect to the determined applied voltage V, the charge amount Q in the sensor portion composed of the electrodes 3 and 4 increases, and the charge amount in the capacitor 10 also increases. Since the capacitance at 10 is unchanged, the terminal voltage of the capacitor 10 increases.

更に、コンデンサ１０に蓄積された電荷は、矩形波の交流高電圧の印加により電界の極性が反転して起こるコンデンサ１０の放電によりリセットされる形となり、また、各電極３，４に付着していたＰＭについても、前記電界の極性の反転により電極３，４側と同じ電荷となって反発することで剥離し、排気ガス２の流れによりＰＭが吹き飛ばされてリセットされる形となり、その後で新たな電界により帯電したＰＭが付着し始めることになる。   Further, the electric charge accumulated in the capacitor 10 is reset by the discharge of the capacitor 10 caused by reversing the polarity of the electric field by applying a rectangular wave AC high voltage, and is attached to the electrodes 3 and 4. Also, the PM is peeled off by repelling with the same charge as the electrodes 3 and 4 due to the reversal of the polarity of the electric field, and the PM is blown off by the flow of the exhaust gas 2 to be reset. The charged PM begins to adhere due to a strong electric field.

図５はパルス高電圧発生手段１１による両電極３，４への印加電圧Ｖinと電圧測定器１２の検出電圧Ｖoutをグラフで示したものであり、波形Ａのように矩形波の交流高電圧である印加電圧Ｖinを印加した場合、電圧測定器１２により測定される検出電圧Ｖoutは波形Ｂのように検出されるが、時間軸を印加電圧Ｖinのパルス毎に分割して、その分割された単位時間内でのピークの電圧値、若しくは、平均電圧値を測定値として制御装置１３でＰＭ濃度に換算すれば良い。 FIG. 5 is a graph showing the voltage V in applied to both electrodes 3 and 4 by the pulse high voltage generating means 11 and the detection voltage V out of the voltage measuring device 12. when applying an applied voltage V in is the voltage, but the detection voltage V out measured by the voltage measuring device 12 is detected as the waveform B, and dividing the time axis for each pulse of the applying voltage V in, What is necessary is just to convert into the PM density | concentration by the control apparatus 13 by making the voltage value of the peak in the divided unit time, or an average voltage value into a measured value.

ここで、本形態例の場合は、温度センサ１４に測定された排気温度に基づき制御装置１３で算出したＰＭ濃度に温度補正がかけられるようになっているので、排気温度による電圧値の変動を加味して、より精度の高いＰＭ濃度が制御装置１３で求められることになる。   Here, in the case of this embodiment, temperature correction is applied to the PM concentration calculated by the control device 13 based on the exhaust temperature measured by the temperature sensor 14, so that the voltage value variation due to the exhaust temperature is changed. In consideration of this, the control device 13 obtains a more accurate PM concentration.

ここで、図６に模式的に示している通り、前記各電極３，４は排気ガス２の流れに対し平面を持たない円柱形状となっており、しかも、排気管１の途中に排気ガス２の流れを横切るように挿入され且つ排気ガス２の流れの向きに並ばないように対向配置されているので、特に前記各電極３，４の対向面は、排気ガス２が接線方向に近い向きから強く吹き付けてＰＭが留まり難い環境が作り出され、電界の極性の反転に伴うＰＭの分離除去が確実に行われることになる。   Here, as schematically shown in FIG. 6, each of the electrodes 3 and 4 has a cylindrical shape having no plane with respect to the flow of the exhaust gas 2, and the exhaust gas 2 is disposed in the middle of the exhaust pipe 1. Are disposed so as to cross the flow of the exhaust gas 2 and are arranged so as not to line up with the flow direction of the exhaust gas 2, and in particular, the opposed surfaces of the electrodes 3, 4 are from the direction in which the exhaust gas 2 is close to the tangential direction. An environment in which PM is hard to stay by blowing strongly is created, and separation and removal of PM accompanying the reversal of the polarity of the electric field is surely performed.

尚、パルス高電圧発生手段１１により交流高電圧の矩形波の周波数を下げて一周期当たりのコンデンサ１０の充電時間を長くすれば、排気ガス２中に含まれるＰＭの濃度が低い場合にも各電極３，４へのＰＭの付着量を有意差がある量としてＰＭ濃度の検出を実現することが可能となる。   Incidentally, if the frequency of the AC high voltage rectangular wave is lowered by the pulse high voltage generating means 11 to increase the charging time of the capacitor 10 per cycle, each of the cases where the concentration of PM contained in the exhaust gas 2 is low. The PM concentration can be detected with the amount of PM adhering to the electrodes 3 and 4 as an amount having a significant difference.

従って、上記形態例によれば、電極３，４の形状と配置を工夫し且つ該各電極３，４に矩形波の交流高電圧をパルス高電圧発生手段１１で印加することでＰＭの付着と剥離を確実に行わしめて、時々刻々変化するＰＭの濃度を連続的に検出することができ、しかも、ＰＭの堆積による悪影響を受けずに正確な測定を長期間に亘り継続することができ、更には、パルス高電圧発生手段１１で交流高電圧の矩形波の周波数を下げて一周期当たりのコンデンサ１０の充電時間を長くすることにより、排気ガス２中に含まれるＰＭの濃度が低い場合であっても、各電極３，４へのＰＭの付着量を有意差がある量としてＰＭ濃度の検出を実現することができる。   Therefore, according to the above-described embodiment, the shape and arrangement of the electrodes 3 and 4 are devised, and the pulse high voltage generation means 11 applies a rectangular AC high voltage to each of the electrodes 3 and 4 to thereby prevent the adhesion of PM. It is possible to detect the concentration of PM that changes from time to time by reliably performing peeling, and to continue accurate measurement over a long period of time without being adversely affected by PM deposition. Is a case where the concentration of PM contained in the exhaust gas 2 is low by lowering the frequency of the rectangular wave of the alternating high voltage by the pulse high voltage generating means 11 and increasing the charging time of the capacitor 10 per cycle. However, the PM concentration can be detected by setting the amount of PM adhering to each of the electrodes 3 and 4 as an amount having a significant difference.

また、排気管１内の排気ガス２の温度を検出する温度センサ１４を更に備え、該温度センサ１４に測定された排気温度に基づき制御装置１３で算出したＰＭ濃度に温度補正をかけ且つ所定の下限温度以上でのみＰＭ濃度の検出を実施し得るよう構成しているので、排気温度による電圧値の変動を加味した精度の高いＰＭ濃度を求めることができると共に、所定の下限温度を下まわるような排気温度の低い結露環境下での不正確な検出を回避することができる。   Further, a temperature sensor 14 for detecting the temperature of the exhaust gas 2 in the exhaust pipe 1 is further provided, and the PM concentration calculated by the control device 13 is subjected to temperature correction based on the exhaust temperature measured by the temperature sensor 14, and a predetermined value is obtained. Since the PM concentration can be detected only at the lower limit temperature or higher, it is possible to obtain a highly accurate PM concentration that takes into account fluctuations in the voltage value due to the exhaust temperature, and to fall below a predetermined lower limit temperature. Inaccurate detection in a condensation environment with a low exhaust temperature can be avoided.

更に、一対の電極３，４のうちの一方をワイヤで構成し且つ他方を前記ワイヤを支持するためのサポート材を兼ねたロッドで構成しているので、サポート材を不要として製作を容易化することができ、しかも、サポート材が不要となる分だけ排気ガス２の流れに対する圧力損失を低減することができる。   Furthermore, since one of the pair of electrodes 3 and 4 is composed of a wire and the other is composed of a rod that also serves as a support material for supporting the wire, the support material is not required, and the manufacture is facilitated. In addition, the pressure loss with respect to the flow of the exhaust gas 2 can be reduced by the amount that the support material is unnecessary.

尚、本発明の粒子センサは、上述の形態例の如きパティキュレートフィルタの入側への適用に限定されることなく、排気管途中のどのような場所に適用しても良いこと、その他、本発明の要旨を逸脱しない範囲内において種々変更を加え得ることは勿論である。   The particle sensor of the present invention is not limited to the application to the entrance side of the particulate filter as in the above-described embodiment, but may be applied to any location in the exhaust pipe. Of course, various modifications can be made without departing from the scope of the invention.

１ 排気管
２ 排気ガス
３ 電極
４ 電極
１０ コンデンサ
１１ パルス高電圧発生手段
１２ 電圧測定器（電圧測定手段）
１３ 制御装置（演算手段）
１４ 温度センサ DESCRIPTION OF SYMBOLS 1 Exhaust pipe 2 Exhaust gas 3 Electrode 4 Electrode 10 Capacitor 11 Pulse high voltage generation means 12 Voltage measuring device (voltage measurement means)
13 Control device (calculation means)
14 Temperature sensor

Claims (3)

排気管を流れる排気ガス中に含まれるＰＭの濃度を検出する粒子センサであって、排気管の途中に排気ガスの流れを横切るように挿入され且つ該排気ガスの流れの向きに並ばないように互いに平行を成して対向配置された円柱形状の一対の電極と、該電極の一方を高電圧電極とし且つ他方を接地電極として両電極間に部分放電が発生するよう矩形波の交流高電圧を印加するパルス高電圧発生手段と、該パルス高電圧発生手段により両電極間に交流高電圧を印加するための電気回路中に介装されたコンデンサと、該コンデンサの端子電圧を測定する電圧測定手段と、該電圧測定手段により測定された電圧値をＰＭ濃度に換算する演算手段とを備えたことを特徴とする粒子センサ。   A particle sensor for detecting the concentration of PM contained in exhaust gas flowing through an exhaust pipe, which is inserted in the middle of the exhaust pipe so as to cross the flow of exhaust gas and not aligned with the flow direction of the exhaust gas A pair of cylindrical electrodes arranged in parallel and facing each other, and one of the electrodes as a high voltage electrode and the other as a ground electrode, and a rectangular wave AC high voltage so that partial discharge occurs between the electrodes. Pulse high voltage generating means to be applied, a capacitor interposed in an electric circuit for applying an alternating high voltage between both electrodes by the pulse high voltage generating means, and voltage measuring means for measuring the terminal voltage of the capacitor A particle sensor comprising: a voltage value measured by the voltage measuring means; and a calculating means for converting the voltage value into a PM concentration. 排気管内の排気ガスの温度を検出する温度センサを更に備え、該温度センサに測定された排気温度に基づき演算手段で算出したＰＭ濃度に温度補正をかけ且つ所定の下限温度以上でのみＰＭ濃度の検出を実施し得るよう構成したことを特徴とする請求項１に記載の粒子センサ。   A temperature sensor for detecting the temperature of the exhaust gas in the exhaust pipe is further provided, and the PM concentration calculated by the calculation means is subjected to temperature correction based on the exhaust temperature measured by the temperature sensor, and the PM concentration is detected only at a predetermined lower limit temperature or more. The particle sensor according to claim 1, wherein the particle sensor is configured to perform detection. 一対の電極のうちの一方をワイヤで構成し且つ他方を前記ワイヤを支持するためのサポート材を兼ねたロッドで構成したことを特徴とする請求項１又は２に記載の粒子センサ。   3. The particle sensor according to claim 1, wherein one of the pair of electrodes is constituted by a wire and the other is constituted by a rod that also serves as a support material for supporting the wire.
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